I said yes when my gf's friend asked if her cousin is cute
How did your girlfriend feel about it?
I wasn't thinking about my girlfriend and what she could feel.
You should not be saying other girls are cute when you have a girlfriend. She may think you are being disloyal to her.
That is so over dramatic.
It is a possibility. Maybe your girlfriend does not mind you doing it, but to be safe, you should refrain from doing this.