See, this isn't bad since the girl is willing to change for the boy. I like this trope because it's red flags but not the worst. Pretty high on the crazy/hot matrix. High crazy/high hot = worth risking.
Here's a story from my life though.
Back in my middle school days, we had a girl in my class that really liked this guy in the same class. It was cute and all since they were both some of the shortest people in class, but I happened to be friends with the guy.
Long story short, the girl somehow obtained my friend's home phone number (landline) and called it, greeted his mother and told her that she was his friend. His mother thought it was cute that she called to inform my friend of the homework from that day. But it wasn't cute because the girl grew out her moustache (yes it's possible for girls to have moustaches) and made no attempts to change herself. All she had was the yan(-dere) love, stalking behavior, excessive touching in school, etc without the "I would do anything to make you love me back" part. So what you're left with is a stalker. A cute, but now-with-a-moustache stalker. High crazy/low hot = no.