Hooked up with a guy my friend dealt with...?

Ok so last weekend, me and my girls decided to get together and drink then all chill. So me and my other friend were waiting for the two others at a plaza when we heard that they were getting a ride there. So it turned out that one of their friends that was in grade 12 drove them there. were in grade 9 by the way. Anyways so we bought some chasers then went and drank in the car. Me and one of my friends drank the most so we were gone while the other two were drunk but didn't have as much as us. So we ended up hanging out with the guys who drove them there along with the guys friends. That night, i hooked up with the guy who drove my friends there. Hes in grade 12. I didn't know who he was but i met him that night and since i was drunk, we hooked up. Then after wards i found out that one of my girls dealt with him at the beginning of the year so she started cussing at me and making a big deal out of it. I mean, i don't understand why shes even mad since first of all, they didn't even officially date and on top of that, she has a boyfriend at the moment. So i was like what the hell but i apologized and told her that i was drunk but were good now. Now the problem is that when i hook up with guys, i cant just forget about them after wards, I need to talk to them or something at least but im scared that if i like his picture or something on facebook, my friend will get mad at me again. Help? lmao what a messed up story :$