I'd be more worried it Mutsuki had given Aya a ring and they suddenly stopped showing her wearing it. As it is, I'm more inclined to put this up to the authors occasionally rough storytelling skills.
Still, with how long it took us to get to the actual yuri, it would certainly be an unnecessary level of drama to drop now, least of all with no explanation as to when and why they suddenly have broken up.
"Way too much silly drama for far too long."
Oh, I agree there. Though I don't necessarily blame the author for it. I've dropped so many yuri manga for having to constantly shoehorn in drama is actually disgusting. Between that and the Girls Love tag being filled with yuri bait (Still pissed at 'Budokan') or more toxic relationship entries (Citrus, NTR, Happy Sugar Life), it can be an actual nightmare finding good wholesome yuri sometimes. Thankfully there's always Kase-san to fall back on. Though even that author likes occasionally slipping in unnecessary levels of heavy drama.