Stealing directly from Nettie also causes issues with the druids in the Druids' Chambers. Although party members can leave initially after the theft (successful stealth and sleight of hand by Astorion, had him QT out, then everyone else walked out normally/no interactions), when returning to talk to Nettie, everyone in the Chambers is hostile.
I imagine this is due to stealing the circlet and/or poison, though. And it kinda messes up her ability to poison you and open the back chamber. Not 100% sure on this, though.