I have a crush on my friends girlfriend
Why do you have a crush on her?
She's really beautiful and I'm jealous of my friend.
I'm sure your friend's girlfriend is very pretty, but it's wrong to have feelings for her. You need to respect your friend and accept that she's his girlfriend and off limits for you if you want to preserve your friendship.
Nah. I don't care what my friend thinks. I'm going to make my move soon.
That is incredibly selfish. What if she rejects you and tells your friend? Then you will look like a jerk.