When the Extras had frozen in their spots and refused to respond to any external stimuli, Vala's concern had only been fleeting. There was clearly nothing that could be done, and she's been in Taxon long enough to know that these things tend to just rectify themselves. Anyway the point is that Vala decided, somewhat spontaneously, that it was the perfect opportunity to return a favour that was long overdue. And by favour, she means the fact that she'd been caught cheating at cards in a certain bar in Taxon, which had led to her starting a fight, which in turn had led to her being thrown out (quite literally and certainly not gently) and barred.
Vala's already precariously balanced psyche has been slowly deteriorating ever since Daniel left, and then when Jack followed - the effect of long-term incarceration in Taxon and the various glitches that have affected her and others close to her really started to show (when she was away from the SGC and Mitchell at least). Not that she'd attribute the timing of her relapse to any of that, not consciously anyway.
In the middle of a bar full of frozen Extras in Osten, Vala is shooting the rows of bottles and glasses behind the bar with a
P90. She seems unaffected by the destruction she's causing, nor is she flinching when the shards of broken glass embed themselves into the unresponsive Extras - if she even notices. What did it matter? They weren't real people, they were just empty shells. Even if they had been real once - they definitely weren't anymore. Taxon had stripped them of everything, maybe that's what it did to everyone in the end. When she's sure every bottle and every glass is shattered and all the mirrors, the gun falls limply to her side. She walks calmly out of the bar, wiping the tell-tale stray tears away with the back of her free hand.
[[OOC: Backdated to when the Extras froze - OBVS. Vala's been here nearly a year and it was time a few cracks started to show. She's not known for being the most emotionally stable person ever - despite the front she wears most of the time.]]