Chill with the accusatory tone, man. For real. It's also a bit weird to imply what people have said and done in the past as part of getting to know them just stops mattering in a discussion involving your belief that the two are inconsistent. If it doesn't matter then the supposed inconsistency doesn't matter and the discussion is pointless.
My bad on misreading that it was about Halsin. I thought you were talking more generally about her characterization.
It doesn't stop mattering, but like I said in the post above, it shows that they've changed throughout the story.
Lae'zel will have sex with you casually in act 1 and says it's nothing more than that. She doesn't care if you bang Astarion on the side. Lae'zel in act 2 falls in love with you and wants you for herself. That implies character development. It shows she has changed. To then have her be okay with you having a relationship with Halsin in act 3 all of a sudden and say "well, in act 1 she was okay with it?" is ignoring that character development she went through. That's what I meant.
Similarly, Shadowheart flirts with you in act 1 and while she declines attempts at making it open at the party, she evidently didn't flat out say "no". However, she does flat out say "no" in act 2. Therefore, the act 1 interaction is replaced by her character development, so it can't be used as an argument for her saying yes in act 3.
Or, honestly, to make it even more simple, here's an example.
Lets assume a companion says "oh I'm up for an open relationship" in act 1. As the story goes on, they fall in love with you. In act 2, they'll say "nevermind, I'm actually not up for that, I didn't expect to love you as much as I apparently do". To then have them suddenly be okay with it again in act 3 is inconsistent, even if they were okay with it in act 1. Unless they stops loving you as much. Which needs to be mentioned, implied, written down.
