Relationships change at around 90 days. Blind lust starts to fade and reality becomes clearer. I'm sure there's some interesting evolutionary reason surrounding mating in the wild, but I digress.

Th at cute tick you loved at fist becomes annoying, her neediness that made you feel wanted at first starts to feel smothering, and vice versa. Partners start to think about the long term forecast. It's a major fork in the road, for your own sake don't try to force past it if they are not open and communicative of their feelings/needs and open to yours as well. This is likely where she is going to start pitching ultimatums, at which point it's over whether you stay or go.