I don't see Shadow setting boundaries tbh. There is this dialogue combo where Astarion asks, if the others have sweethearts waiting in BG and Shadowheart is like ' eww - relationship. I just seek sex and move on' . She says it more eloquent, but it makes it pretty clear, she is a free spirit.
She have that line, yes. But what I saw in her development through her romance arc is that she wasn't emotionally connected with others until she meets your character. You know about that, about Shar practices, yet she seemed like she genuinely wanted escape from all that and find something completely different with you, she doesn't sleep with you outright, and to you personally she tells you about not wanting to be a spare lover. She goes that route from "ew, relationship" to finding someone she would be willing to live happily ever after. And being finally emotionally connected and having emotional affair at the same time seem so contradicting and simply insulting to the main character.
Is that dream line from the brothel? It sounds like something from the brothel, when you initiated the fivesome.
Without wanting to be contrary, to me it shows your character is enough for her in all regards because, even though she might have had some sexual fantasies about Halsin, she ultimately doesn't act on them, she doesn't even bring them up unless you initiate something. (Although this probably depends on where on the scale of betrayal that flirty banter falls for you.) That sounds like a choice to me, especially for someone who in act 1 scoffs at longterm bonds and is in favour of short term amusements. But I might be missing something because I only know her romance until act 2, where she gave me flirty greetings but also put her faith over romance.
I wish I could perceive that as lustful lies, which could be easily avoided. But that banter just confirms that what she said there was true, they speak about your intimate moment and she would be like "Yeah, sure, come along next time". And that happens if you have an imprudence to take them both to your party, while romancing Shadowheart even if you have been faithful the entire time. That made my Tav look like obedient tradwife, who doesn't have a word in the relationship. Maybe my character fell for the wrong one in the end.
