Just tested this out, and same thing happened to me, she also won't get off at Zheng Shi & Dhaal either, which is kinda weird considering her group is also there on Zheng Shi. I don't know how the coding stuff works (although that's not to say I ain't interested as I'd like to take a crack at it), but I think she's just programmed to get off at any spot that is safe for the PC and isn't removed from the game. She can get off at every location besides Uveto and Zheng Shi it seems.
Or maybe she hadn't been properly updated, and was added in after Gastigoth, but not Uveto and Zheng Shi, hence she gets off at any place that her version allows. Though that doesn't explain why the person who added her into the game allowed her to get off at Gastigoth.