I want to yell at my girlfriend to stop talking about me with her friends.
What makes you think that she talks about you?
I've been paying a lot of money for her things, I gave her a luxurious life. She's not even grateful.
I understand that you feel your gf is ungrateful and talking behind your back, but yelling and screaming will not solve things. Sit down with your gf and tell her your concerns so that you can work things through.
Whaaaaaaaat? Are you going to defend her?
Yes, I am going to defend her a little. I do not think that it is right to scream at anyone, even your girlfriend.