Bro, I cannot fathom how you are convincing yourself of this. Words are not actions but they do convey INTENTIONS. Also, considering she dreamt about her interaction with Halsin, already suggests an 'action'. Even if she wants to do that 'Action' she cannot unless they have coded that in the game, so the closest thing we can get is her dreaming of Halsin, and her intentions based on what she is saying. So even if they are just Words, they are all that we can rely on to move forward in the story, showing the intentions of the characters, and what they actually want to do. So no, its also not a "premature conclusion based on some comments" thing, because we know what happens in the game: she dreams of Halsin, disapproves when you do not let them sleep with each other, flirts with Halsin even after her romance is completed. Shadowheart dreaming of sleeping with Halsin, and wanting to get with him is BTW a form of EMOTIONAL CHEATING. I do not know if you have heard of this considering, you may be into this ShadowCuck thing.
But also, the fact that you approve of Shadowheart making "few flirty jokes" to other companions while you are in a romantic relationship with her is just... disgusting. And no her disapproval is just not her getting bad vibes from you, because you are being possessive. At that point of the story, you have already explored her romance and know that you have each other as romantic partners. Let me tell you, it is normal for people to be possessive of each other when they are in a romantic relationship. Shadowheart demonstrates this 'possessiveness' when you try to romance other companions and you are already with her, and will even end your romantic relationship, as she does not want to share you. So bottomline is, she is not disapproving of you because of "bad vibes", wtf that is so shallow. And no she should not be disapproving of you because you are being possessive, that should be normal as the MC and her is in a relationship in game. BOTH Halsin, and her disapprove of you at the same time, because you disagree with them getting together, simple as that, and it is so clear to see. Open your eyes.
As Rotsen has written in the original post, and as I have also written in my earlier post, regarding this Shadowheart threesome and people complaining. Larian could have made it so that for people who really wants to have threesome moment with Shadowheart, they could make it so that she will agree with this kind of thing if she takes the Evil or Shar Route in game, that way her character background would actually be more fitting- as Shar is into doing evil acts, so I would agree if she would not mind having threesomes or orgies, or poly romances. However, they could also have made it so that if players choose the Selunite Shadowheart or the good Shadowheart route, then she will be more possessive of the MC, given everything that she has been through, and would not want to share the MC with others. I think this is the best option Larian could have made.
Dreams aren't intentional, I have no control over what happens in my dreams. What I do when I am awake and conscious is what I can control. What I am saying is that sexual thoughts and fantasies aren't a betrayal as long as you leave them at that.
Whether sexual activities between consenting adults are "evil acts" is a matter of personal belief which is a discussion that I don't think anyone wants to get into. I'll just leave it at that I don't agree that it has anything to do with being evil or not.