okay, it is kind of pissing me off when people insist Vi went with the Enforcers because she wanted to join them and side with Piltover and move up in society, and not because it was the only vehicle available for her to go after Jinx and solve the problem she created
(also, Vi does not want to kill her sister; she is driven by guilt. Vi feels she has a duty to stop further destruction and death from the monster she thinks she created. Jinx told Vi that her sister is gone and only the monster remains, and Vi believed her. After s2ep3, I don't think either of them believe that anymore)
Vi still detests the Enforcers. You can plainly see on her face (and through her words!) that she does not want to be there. She just wants to get this over with.
if anything, Vi was trying to support Caitlyn, who is one of the only familiar things she has in her life at this moment. Her family is dead, she thinks her sister is gone, and the Undercity is barely recognizable to her - but Caitlyn was there. So, Vi took a gamble on sticking with Caitlyn, the seemingly sweet girl from Piltover who has sympathy for the Undercity, sees Vi's good heart, and helped Vi when she didn't need to.
Vi resigned herself to join Cait's enforcers, compromising her morals, hoping to be a positive influence. But the second she made a decision for herself, the second she stopped Cait from shooting a child, Caitlyn discarded her
she's lost, trying to find her footing wherever she can. Vi has been scrambling to attach herself to any scrap of familiarity since escaping Stillwater, and now she's left alone, in the dark, again
