Eh...Kind of Meh, I knew already that the relationship felt toxic from the start and middle ("I will keep going till you know" she said instead of being frustrated or worried about her GF) but the so-called "Twist" is a bit boring and feel weird/out of place. But I guess that is just me personally and it probably would be more shocking to younger inexperience readers though....
It would make more sense if the girl/childhood wanted to dominated and control the MC...The whole line about hating her felt stupid, weird and out of place (Yes I know Hate Fking exists but it still sounds stupid to me)...if it was a yandere-like desire for control and dominance over another person (Weak-willed MC here) then the twist would not feel weird and out of place for me.
I liked 'Untitled Yuri Manga' more where the relationship was messed up but it still had a mostly 'positive' ending in the relationship...Still wrong but eh if the adults are not going to assign those 2 a good professional therapist then they can't complain.
I seen better Yuri twists manga/doujins, not a horrible or bad twist but I felt like it could have been done better. It basically felt like the bootleg one-shot version of that Toxic Yuri Manga that I read years ago that I abandon/didn't finish due to feeling/predicting there was no hope for a good ending. I think it was called Kitanai Kimi something...