I'm annoyed, but the entire theme of this side-story is the series of horrifyingly bad decisions the cafe owner and her friend made in their youth, and why their current relationship is so complicated. It's not the "let's fuck around with scumbags because our true feelings are murky and we need to shake ourselves up before we can discover Twu Wub" show. It's small comfort, but I'm at least glad that the author doesn't assume we like the guy. (Hm? "Am I still mad about that"? I couldn't possibly know what you mean.)
Person saying it's consensual because she agreed: yes, she agreed under false pretences, after he figured out that he could effectively hold the other girl hostage to trick her into doing what he wants. At best, that's a cartoon villain forcing someone to choose between killing a bus full of orphans or their lover; more realistically, it's coercion. And anyway, this is the guy who's entire introduction to the story was trying to rape a girl while she was unconscious. Are we seriously concerned about not being sufficiently charitable towards his moral standing? C'mon.
By no means was I trying to be charitable towards the guys moral standings, he is a complete scumbag, and it may not be legally criminal, but what he's doing is morally and socially criminal.
I was just saying that she does have choices in this situation that don't involve her sleeping with him. She's not seeing these options because she's really only concerned about her feelings. She's not trying to save her friend from a bad guy, trying to punish him, or doing this for any other reason than she wants the other girl for herself. Her judgment is impaired and she's making a really bad decision not from the obvious coercion, but from her own errors.
I also don't like the implication of saying she's being forced to do this as if women cannot decide these things on their own. That said I do believe that depending on the situation coercing someone into sex is the same as sexual assault or rape.