Jennifer did such an excellent job as VA for Shadowheart in moments where she is genuinely disappointed, sad and insecure that I do not buy that she is meant to portray any of those things during the Halsin/Twins/Mizora scenes. The only thing she sounds remotely annoyed about during the Mizora thing is you not asking first, the others she positively encourages.
So no, I still think they're all just completely out of character. However, Halsin is perfect Orin bait if he's alive until he gets more act 3 story (which might never happen), drows can just be ignored like any other NPC in act 3 and Mizora.. well you brought it on yourself, you act out of character, she acts out of character.
Yeah i agree, even though i still think her being ok with Tav cheating and wanting foursome with twins is out of character, that still can be explained, she was brainwashed, memory wiped all her life, she didn't experienced healthy long term relationship (only casual sex). Also as you said you brought it on yourself by cheating. So i don't mind that.