The direct entry to trade from dialogue with Shereth only happens the first time you talk to her.
After that, you have to click Trade, just like everybody else.
Of course if you talk yourselves into killing her for being a dirty Sourceror, you can't trade with her any more. Just saying.
Oddly enough, Madora doesn't have any problem with not killing her.
- Cats: bad.
- Deaf people: bad.
- Wizards and magic: bad.
- Nobles who can't keep it in their pants: bad.
- Self-confessed Sourcerors and thieves: Perfectly OK! Lovely woman! Let's all have cake and balloons!
I'm hoping there's some effects on henchman attitude from party choices coming in the full release.