Look at it this way. All that there is in the game only suggests that Shadowheart is not fully monogamous, she is open for some experimenting.
Nothing at all implies she isn't fully monogamous. She remains fully monogamous after these interactions, and she was before these interactions. They have absolutely zero story impact. I'll quote the line she says if you suggest an open relationship with Wyll again: Shadowheart: In truth, I don't think I'd want to be your spare lover. I'd always want more of you than you'd have to spare. Better perhaps to bow out with dignity.
If that doesn't indicate monogamous, plus her actions (declining an open relationship with ANY of the other companions, even those she was actually flirting with) then I don't know what is. She wants you and she doesn't want you wasting energy on anyone else. That's monogamy talk. And that's just one of many examples, while nothing ever implies otherwise.
Originally Posted by Frog001
In drow twins discussion she says "If you are comfortable sharing, so am I". Halsin butting in and everything else happens only after player says "Yes" to that, which indicates being comfortable with at least some sharing.
You conveniently left out the incredibly suggestive "Now there's an idea..." she also says when the twins suggest it without you ever asking them for sex. I hope you realize that in a situation where your love interest pushes for a night of pleasure with prostitutes (no matter how out of character it is for her to do so), some people will feel pressured into accepting. The rest of the dialogue is unavoidable the second you do and as I said in the post above, is grounds for divorce/separation and people have quit the game over it.
Originally Posted by Frog001
Although disapproval if you refuse Halsin doesn't make sense and has to go. It also doesn't make sense and has to go for Astarion too while we are on it.
Yes. Both Astarion and Shadowheart have had part of their character ruined because of the late inclusion of Halsin's creepy romance. Thankfully it's all avoidable by not bringing Halsin. But not everyone knows that bringing Halsin will ruin their immersion.
Edit: But the disapproval isn't the only problem. It's what she says before that already.