I think you're wrong about the part of her doesn't remembering, in the Mizora scene she says that even with the little she can remember, she can tell us stories. So, I wouldn't say she doesn't remember. It sounds, if anything, that she got lots of sexual experience.
But to be fair, I'm saying this from the top of my head, and don't got time rn to double check that scene. I may be wrong.
It is mentioned during the Mizora scene, yes. Now, I consider the Mizora dialogue only written to fit the Halsin narrative, so I'm taking it with a grain of salt.
But lets assume it is correct, she still only remembers the deeds. What she doesn't remember is that she kept straying, because that is what they kept wiping from her memory; the part of her that didn't want any of it. She was - for all intents and purposes - being
raped
, repeatedly, if we're going to take the Mizora chat as canon. (I think you all know what word is there but some might not want to read it)
If that's what they want to imply, they're free to, I'm not averse of talking about heavy subjects. It still doesn't fit the person she becomes with you throughout the story, therefore she still shouldn't be okay with sharing or you cheating, by the time you get to act 3. Your Dark Urge butler tells you some pretty disturbing things about your own past. The knowledge of you doing those things doesn't make you that person now.
The problem with Mizora is that you have control over situation and this happens only if you want to, Shadowheart's reaction to this is ok. But you cant for some reason control situation with Halsin(bugged or not) with their banter and drows fivesome.