We'll se what are the consequences of this choice. I could understand Sage being disappointed and willing to downgrade her relationship with the MC if he chooses to go with Jill's date instead of helping her, but I wouldn't understand that kind of move from Jill. I mean, in real life, this is a no-brainer and any normal person regardless his DIK/CHICK alignment would go and help his friend, would tell the other person what's happening, and unless this other person is utterly stupid (which we think it's not Jill's case, at least before the whole blackmailing thing) everything would be fine between them.
That's what some of us don't like from DPC and why we don't support him on Patreon, because there are lot of moments like this that break the immersion for us. He offers you a choice here, but doesn't allow others that would mean a real conflict for players, like going to Jade after getting M&J, thus also blocking Cathy because reasons, and some more of that kind. He just blocks some paths without a clear or even logical in-game reasoning, while offering brainless choices that leads to some over the top drama. It's great to have branches instead of a linear development but when those branches aren't well thought (or, at least, players can't understand their logic) you are not making it any better