SPOILERS AHEAD (duh).

I attacked some pirate bases and at the bar in the "good" pirate station a new character appeared - Vaal. She asked me if I would attack pirates again and when I confirmed she asked to join my crew. I agreed and a big text appeared saying "Vaal recruited" (or something like that), but she's still in the bar and when I talk to her she responds with "Get lost". She didn't appear in the bar at my station.

EDIT:
I restarted the game, got back to the pirate station and she was recruitable.