I think it's "Suika spilled alcohol on Alice, Alice expected her to go seme (like everyone else) and sexually assault her. When Suika didn't Alice couldn't help hugging her for her kindness... Reimu sees this and shows her semi-yandere side again"
I think I know what happened to Alice to cause all this in the first place.
Remember what Suika's ability can do . . . ?
For her to run into so much of the cast, and neither Yukari nor Eirin were behind it . . . it had to have been . . .
Rei..mu?I told you not to drink sake on top of the shrine gateway.Huh? You reek of sake too.I don't think that's something to bathe in.Huh?Why not, it's warm up there.