Comedy gold.
Yup. That's the stuff I come for at this point. What a weird, forced reason to initiate this development, "the >bad< girlfriend is suddenly absolutely miserable with directions oh no". The first part of the chapter was actually quite cute though, against at least some of the odds.
I wouldn't call her asshole-ish, I'd call her... passionate lol. She's obviously flawed, I'd imagine she's been working through the last few chapters' events in her head wondering what she did wrong. Wouldn't be surprised if "being too demanding and confrontational" comes out as the conclusion, she pushed to try to end things definitively before Yuni was quite ready to move on, which shows Fuuko in retrospect to be less manipulative than she previously came across as. She wasn't winning because she's a puppet master making Yuni dance to her tune, she was winning because Yuni really did want her, and she stopped winning because Yuni flinched out of guilt for being a "cheater".
Yes I do actually agree with a lot of this. But also, chapter 17 exists ahaha. I call that crossing the line, you call it being passionate, but hey it's all good.