meh, the tired trope of "old friend secretly always in love with an MC" who only confesses when it's so clear she'll never be accepted.
I mean, it's not necessarily a bad trope per say, but it's just so damn overused in yuri manga that it's just get over with this dumb point we all know will lead no where, and progress the main couple pls
After catching up, I really think it's purely because she feels she's losing her and is scared of that. Until now, she was always able to visit Asahi and Subaru at will, but if Asahi moves to Hinako, the whole visiting thing will become more difficult and they might grow more distant - especially with how awkward the dynamic between them has been already.
It's a trope and kinda overused, I agree, but in this case I really like the timing of it, feels very natural to me - she's grasping at straws, feeling desperate and that she has nothing to lose.