Honestly at this point, they should just add dialogue with SH(and other romanced companions) about setting up boundaries and what you expect in your relationship. Shadowheart is flexible so you should be able to chose both routes(mono and poly) and she should be ok with that. That way both groups of ppl would be happy. Maybe also change her reactions to certain situations(like mizora for example) based on chosen "route".
SH isn't "flexible" until Act 3 though. Again, it's inconsistent with how a lot of ppl view her character in acts 1 and 2, so it would look like they're retconning her. Most ppl don't like retcons, in most cases.
Though I suppose in act 3 she already is retconned. So either way, Larian has shitty writing.
