Headcanon
So what is with Martha and the movies?
When Martha was a kid, and her parents were fighting, she would go and collect Tish and Leo and they would all bundle onto her floor with blankets and pillows and watch movies at loud volumes, often falling asleep together in a pile. As they grew up, they didn't do it so often, but a blanket and a movie became Martha's default setting when things were very stressful and she wanted to attempt to relax.
After the year that wasn't, Martha and Tish spent loads of nights together doing that, and doing it would lead to Tish talking about what happened. Movies are therapy to Martha, so when she was dealing with things aboard the Barge she would watch them.
So what's all this about PTSD?
Well, Martha Jones spent a year walking a hellish distopia where she was hunted by silver deathballs, the Master's death squads, people who wanted to turn her over for the reward, and general horribleness. She went without sleep, food and proper medicine. Above all else, Martha Jones is a doctor, so everywhere she went, she tried to help people, and in the end watched a lot of them die around her.
What I think a lot of people forget is that the Master killed 600 million humans in the first hour of his occupation ("decimate them. Remove on tenth of the population.") This isn't counting the people whom were worked to death, killed for fun, the resistance, radiation pits, radiation sickness and everything else. I think that probably the Master reduced the population of humanity probably by at least 2/3rds given everything especially the descriptions of Europe, Russia, China and America, which all have huge populations.
Also, there was the way the Master removed Japan from the map. He burned the entire thing and everyone on it. Well, everyone but Martha Jones. She was the only person to get out of Japan alive, and even then she only did so because someone else put her on a boat and shoved her off. Martha was wounded by Japan, and she carries a plasma burn scar on her thigh and a large scar on her side from where the Toclafane almost caught her.
No one goes through that without coming out scarred on the other side, and Martha Jones hid her scars as she took care of everyone else rather than herself. She took care of herself in leaving the Doctor, but she threw herself into caring for her family and helping them get over it rather than helping herself.
For the first six months she was home, I believe Martha slept with her shoes on so if she needed to run in the middle of the night she could. Also, I believe she kept a bag full of food, emergency medical supplies and water ready always. Just in case. Even now, she still does this to an extent, and if anyone were to actually go through her whole medical bag? They'd find this out.
So Martha kept having nightmares and sleepless nights and not talking about it for the entire time she was home between then and JE, and then for her first four months aboard the Barge. It was only after she was tortured and killed by the Master and Baby Firefly did her PTSD issues come to the forefront. The reason that they kicked in so strongly was because that was Martha's nightmare during the year. That she would fail and that the Master wouldn't kill her outright, or even kill her in front of the Doctor, but that he would torture her to death and no one would ever know.
Following that, Martha had horrible nightmares, didn't sleep for weeks and didn't actually get more than five hours of sleep for months. It was because of this that she started the two am movie club, which continued until her getting involved with Snape.
When she's with him, Martha sleeps and feels safe.
On Martha Jones's screwed up love life.
Or why it's horrible to travel with someone who screws up your self esteem for two years.
Martha Jones is the sterotypic middle child. She's always had issues with being seen and needing attention. For Martha, it came out in her being the caretaker for her entire family. Our first viewing of her is actually her dealing with everything and being the peacemaker within her family. So, she's always wanted people to see her and find her special and wonderful.
Also, Martha Jones does have a type: her type is pretty much "older assholes who need to be fixed." It's been her type since she was a kid, and Martha dearly loves to fix people (or at least try to fix people) as often as she can.
She falls hard and she falls quickly, especially when it comes to someone who is her type. When coupled with the fact that it seems like someone's seeing her? The fall is at least twice is hard, and that's what happened with the Tenth Doctor. He saw her, he found her special enough to listen to his duel heart beats (which he can definitely hide considering no other doctor at Royal Hope seems to have found them before) and then he calls her brilliant, tells her he's an alien and he kisses her tasting of time and forever.
Also, he goes back in time for her in order to impress her.
But then he spends the next two years pretty much telling her that she's second best, her feelings aren't worth it, that she's not as good as Rose all while simultaneously chatting her up at points. He plays it hot and cold, and it would drive anyone mental, but she stays anyway. He also puts her in some of the worst circumstances that one can imagine, and Martha stays because she believes in him. (Taking her and making her a maid in 1913? That would be horrible for any women, never mind a Person of Color who is well educated and comes from an upper middle class background.)
Martha walks the Earth based upon her belief and her love for the Doctor, and after spending a year in hell, she tells him how good she is. It's important to note that even at this important meeting where Martha has saved the Universe's collective asses, Ten is still a dick to her. "Is this going anywhere?" ETC. I don't care how broken he looks when he hugs here, there was still little jabs against her even after she was brilliant. "So this is me, getting out." A brilliant moment, the best moment.
But then there's Tom Milligan or: "Rebounds don't work, especially if they don't remember dying to save your life." I'm going to preface this by saying that Tom Milligan is a brilliant guy. More than that, he's a good man who genuinely loved Martha and Martha genuinely loved him. However, the problem is that they were together for the wrong reasons. During the Year that Wasn't, Tom not only died for her, but he saw her. He saw her through the perception filter and that amazed her. So she was completely predisposed for falling for him anyway.
Then he died for her. Loads of people had, in one way or another during the year. But she stood face to face with the Master, and he was about to kill her and Tom came running out to save her. There was no way that he wouldn't be killed, but he did it anyway. A part of her felt like she owed him for that.
After a "causal" bumping in of him (instigated by Tish) Martha and Tom started dating. For a while their relationship was brilliant, and it was just what she needed, but eventually it began to wear on her that she couldn't tell him about what she was doing and who she was doing it with. She couldn't tell him about why she had nightmares and would get out of bed and just sit in the living room and watch movies with the sound off.
Upon her return from Torchwood, Martha almost told him about it, but then she remembered what had happened to her parents after she'd exposed them to it, and couldn't bring herself to do it. She couldn't bring herself to talk about how Owen had died for her, and she started to pull away from him emotionally then. That would have been more problematic, however he had joined Doctors Without Borders and was gone. The two became engaged as she was dropping him at Healthrow, and though Martha couldn't picture the two of them getting married all that easily she didn't want to lose him and then said yes.
For the last eight months of their relationship, the two were spent in different hemispheres, before Martha came to the Barge and they were in different realities. However, she'd stopped wearing her ring before she'd broken it off with him, and journeyed home just to do it, on Snape's advice. (Yes, yes, he was her best friend well before they got involved.)
Then there was the Fifth Doctor. Martha became friends with him (as she tends to try and do to everyone) and then there was the Kissing Town port. In the Kissing Town port, the two ended up drinking tea with a love potion in it, and they got married. (If you've seen The Tenth Kingdom you'll know this is entirely the norm for it.) After the effects wore off, Martha and the Doctor still had feelings for one another. They tried to avoid it, but in the end they ended up getting together anyway.
This relationship was adorable, but it wasn't healthy. The Doctor often left, and Martha often acted as a caregiver or a pet rather than a partner. They did love one another, but it was definitely doomed to fail given the fact that he would leave the Barge to regenerate. Not only would he regenerate, but he would need to forget about her in order to maintain the timelines. (If Ten remembered her and acted how he did, Martha would have probably never ever forgiven him.)