It's not that it offends her. It's that she can't tell if it's a trick or not which very well come with the explanation she's offering. And if her experiences in Chicago thus far are any indication, she wouldn't have trusted what they said anyway. She isn't really sure if she can't trust him either, but she won't rip out his jugular either.

She doesn't say anything, just slowly exhales through her nose as she faces him and crosses her arms in front of her chest, before raising an eyebrow, waiting for him to explain. Okay. She's listening.

(Sometimes, she is so Derek's sister. Unfortunately, Alek won't appreciate that.)