Is this a stupid reason to feel idk rly upset?

So this one girl keeps texting and commeting on my boyfriend's fb. And I'm not overexagerating, three people have come up to me this week to ask me whats going on and I just laugh it off. An than this week she told me she told my bf to have ppl over today, the one day i could actually spend time with him. SO i told her w.e., i was mad but i wasn't gonna start something over nothing. Than today she calls him to go sledding with him and his two other friends, well they went and still are sledding while I sit here waiting. So yea im upset. Like she invites herself over to hang out with him and its just rly getting to me, and the fact that she's sledding with him with other girls while im at home, and he tells me ill text u when were done just pisses me offf to the upteenth degree. Like i want to say, lets hang out another day im busy.