I like my friends girlfriend
Do you like her as a friend or do you have romantic feelings for her?
I really want to have a relationship with her.
There are plenty of fish in the sea. You shouldn't have feelings for your friend's partner. It will ruin your friendship.
True friends can survive. I want to make her my woman.
You are making a lot of assumptions - your friend's girlfriend is with your friend for a reason. She probably likes him, and trying to pursue her is going to hurt her and your friend, and will make your relationship with both of them uncomfortable. It's better to look elsewhere for love.