Yeah it is mostly things that dont really matter the ones holding it back. As you said, girls can have a past but we dont need to know all the details about it. And since they are not going to be fucking the whole town anymore ( hey, at least brooke was getting paid
) why does that information even matter, unless you are going to be introducing a plot in which they deal with their STDs collection, come on now lol.
Brooke could be ok being a no sex scort for events, that doesnt mean she is a virgin nun thats never seen a penis, it just make her more appealing as she is no longer selling her body for cash to whatever sick fuck that could pay her. That doesn't mean she didnt have relationships, bfs, one night stands, she could have had those, but they are no longer relevant now that she is going to start a relationship with MC alone right? So why even mention them.
Same for Isabella, her past could be that she never had a meaningful or serious relationship, and just met some people here and there but she is now looking for a serious partner. Thats normal, but why exaggerate and make her just a cum dump that was used, abused and then left for a better option. Why would that make her appealing for the MC when even those thousands of NPCs just saw her as a quick fuck and no relationship material? I mean, I agree with those NPCs because a woman like that is indeed no relationship material.
Lastly the cheating gf, there is no redeeming her, even if she was under the effects of a drug, drunk or whatever. The only acceptable way is to make her avoidable, I have never seen, in 100s games I have played, a cheating gf that was liked or redeemed. I have seen a LOT of devs try though, and they all failed. Just check the thread of the game "Fallen roads" if you want to see a miserable attempt at having a cheating gf as a LI. Dev tried again and again till the game ended up abandoned