Getting lucky with busty friend at party

You're at a party with your friends and have to talking to your friend's girlfriend all night. Eventually, you both get fed up of the party and retreat to a calm room, just the two of you. She sits down on the bed and continues talking to you about the overwhelming party atmosphere and how she's really just there because her boyfriend wanted to go. Then she changes the subject. She emphasizes that you are alone, together, and she knows you've been staring at her tits this whole time. She thinks it's just normal and offers you to ask her questions about her tits as she rambles on about never really wearing bras... "I can show you them if you don't tell my boyfriend". Things escalate quickly when she asks you to see your dick since you've seen her tits it's only fair, right? She asks you if you can play together and climbs onto you to ride your dick in cowgirl. She can't have you bust your load in her pussy though... So she tells you to cum all over her huge breasts.