Fade to Silence

Vic is an event based follower. When you are first exploring the zones the game will add an exclamation point to the map, and you'll be prompted that you discovered an event. You'll know it is Vic's event if you see a follower near a treasure chest and a ripper.

Don't go up to her until you have crafted a bow you are okay giving her. If you start the event, but walk back to the refuge the event can end up resetting, and you'll have to do all the steps again.

The event starts at the first chest, Vic will break her bow and leave you to fight a ripper. Once you find her again there will be two more rippers to fight. After dispatching all the enemies walk up to Vic and hold A to interact. You can pick your dialog here, after a few bits of conversation offer to craft her a bow, or give her your own this will result in her deciding to stay with you. When prompted accept her into the camp.

The followers who join you via events are somewhat randomized. Vic's event may take place in the Flats, but for your play through another follower event could be there instead.