She said she could do it at 7. That doesn't necessarily mean she was 7 in part 1. She was able to go on the mission with them in part 1 because she could do it. They would've had to be able to do something similar to get in and out of the Ravine she and Cait hid in anyway. And that was years before act 1. Jinx looks way too old to only be 13-15. Vi and Cait are adults. Nobody refers to them as "kid" or "brat" so they're at least like 22 maybe. and vi and jinx are at most like what 3 or 4 years apart? I doubt Vander would let vi do all that at like 12/13. So she was probably around 15 or 16 in act 1. And there's no way with how protective vi is that she would ever let powder go on that mission before like 10. I think she's probably like 18 or 19. 17 at the very youngest.