It's probably going to be a guy she's set up with. If I were a sociopath like Matsuri is, that's how I'd have it anyways - Yuzu likes Mei, Mei likes Yuzu, they're both girls - makes sense that it'd be a guy to drive the wedge even deeper.
As to whether or not anything will happen, I honestly don't know. I'm hoping that it doesn't, and that Yuzu will find out at the last moment, but considering what happened with the sensei earlier in the manga, I have my doubts.
To be fair, I'm more confused as to why Mei would even give a shit if Matsuri has a photo of her or not, she seems like the type who honestly wouldn't care...
I guess we'll see how it goes.