Trio friendship problem

This sounds like a stupid primary school friendship problem but I really don’t know what to do. Everyone in my class is very very set on who they are friends with so you can’t really move around. I’m in this trio that I’ve been in for 2-3 years, with person A and person B, but I know that Person B definitely likes A more than me. I didn’t think this was initially a problem, because we all hang out and B and I are still friends, but recently I can tell B is almost trying to get me out? For example, we would do one of those stupid ‘what percentage you love each other’ tests in class and I put me and Bs name first, then A and B’s and B said: why is it lower? Me and A should be higher than with u. It sounds nitpicky but theres so many other incidents, where B will say “let’s go together A” and then say “oh you can stay here and wait for us”, or when I had somewhere to go, and B would say: yay, me and A get to do ___ together! When we were initially doing it together. Idk what to do anymore because I can’t stand it. Me and A are good friends, and it’s not like B is actively saying “get out of here” but I have no one else to go to so I’m forced to stick with them. What should I do? This really does sound dumb, sorry 😭