Since they weren't sure of what Party that strange individual belonged to, Shingi decided to move towards her alone. Doing so would be able to tell many things by how she would react since he didn't plan to hide how he looked.
If she recognized him, there would be a great chance for her to work for Mikhail. Dark Guild shouldn't have a good description of his, as he hid his appearance each time he encountered them.
Mikhail should have informed his people about him, and it wouldn't be hard for him to let them somehow know how he looked in great detail.
If she didn't recognize him, she could be working for the Dark Guild, although until now, any NPC that worked under them had a Slave Mark. He checked for one and again came empty-handed, as did his check for Mikhail's mark.