I feel it's very cringe when people try really hard to be cute, and my best friend is one of those people.
What about trying hard to be cute drives you crazy?
It comes off as fake to me.
Such behavior can be irritating. It's a good idea to talk to her, but in the end, if you want to be her friend, you'll probably have to put up with some irritating behavior.
I bet no one else besides me thinks that she's cute.
Well you shouldn't be so critical about that, I'm sure there's other people that think she's cute. Like I said it's okay not to agree with everything your friends do. Maybe communicating this with her would be beneficial.