I don't think she actually tracked him down.
1. The MC was masked when going after the traffickers
2. The only interaction between the captive girls and the MC was him opening the container (I think?)
3. Gemma (our FBI contact/fuck buddy) wants to keep MC's involvement on the down low, I wouldn't put it past her that she took the girls' statements and then told them to leave town, and start fresh. That's one way to make it difficult to bring them in for further questioning.
So for now, I'm seeing her appearance in Lost Solace as a coincidence but will probably keep her at arms length until we find out more.