ignoring the halsin stuff ( the one party banter line and what she says in the 5some) which is obviously some writers pet shit and completely out of character assuming she is romanced, nothing is said by the party member about sharing when talking to the drow unless you actually accept the proposal brought up by the drow twins, only after that does anyone including halsin speak.
As for why shadowheart would agree, potionbeans interpretation works best and very much is in line with her character, she spent her whole life trying to appease shar and mother superior she will do the same for tav, its why she doesnt dump your ass for cheating but says to ask her in advance and mentions past experiences(to make it even and possible stir you up) or declares her non jealousy(she is) all in a disapproving tone while putting on a strong front. The brackets are there cause reading reddit it seems people actually think she was fine with you sleeping with mizora and cant read tones...
Yes, she is emotionally traumatised. After a certain point in the relationship she would let Tav stomp on her face as long as it made them happy. She will agree to every whim that strikes Tav as long as she gets to keep them close. She is the cuckold in the standard Tav-Halsin-Shadowheart poly romance where she urges Tav to sleep with him and then tell her about it. She has all the red flags of someone who could end up in a really bad abusive relationship and the type of bff that I would keep a very close eye on and try to protect from getting involved in a destructive relationship.
And how someone would come to the conclusion that she has a stronger attraction to Halsin based of three lines of banter out of some cheesy harlequin novel, compared to the hundreds of lines of dialogue where she throws herself at Tav seems a tad bit...insecure...
