There is a variable when slut Holly comes to Ian's and Ian asks about her situation rather than immediately going to fuck. Then after they fuck, if Ian selected that option, he will think to himself about how he is worried about Holly's situation.
Given this and the fact that Ian offers to let her stay more nights at his place and Holly says she'll keep it in mind, I wonder if we will get a romance option for slut Holly or if she is too far gone in her hedonism.
If there is a romance option, it will be interesting to see how it interacts with Lena telling Mark that she will try to get Holly for a threesome. We will see from Lena's perspective how Holly feels about Ian and if she will reject Lena and Mark in favour of Ian, similar to how she rejects Ivy's manipulations earlier if Ian showed interest.