Yeah, I definitely saw this moment more as jesting between friends. If it really was a case of one wanting more attention than the other, either one of them could've just hooked the MC into staying with him in his room. These two have the friendship vibe of girls who sit around and just constantly call each other "bitch" without really offending, and I think it is pretty obvious when at the end of the scene they both elect to share the bed with their conquest for the night. Also worth pointing out just how in Mel's corner Sarah is during the Sorority party when MC starts sniffing around about who invited Chad/Sage inquiring about who Chad might be sleeping with.
I went full simp on an Other's route. When Sage asked for best butt, I said Sarah. When I snuck into the Prep's mansion bathroom, it was "I'm looking at Sarah." When Quinn asked who I liked best, Sarah. Then at the dorm party you get that little line of "It's not the first time you've said that about me to other girls..." and it looks like that shell might be cracking.