Plans can always change, but as far as I recall, they don't want MC to be locked of the prom by these choices.
As there's Yumi connected to their story, too, you'd probably get one branch where it's mainly about Helen, the nun and a scene or so for Mia (as some kind of naughty friends with benefits end or so) and one where Harold gets back with Helen and as such MC gets together with Mia and there's the possibility to romance Yumi.
But we'll only know once they actually release it. DC tends to change his mind on these things at times.