Ranting here about my friend of 4 yrs

Ok so we have like a trio, I have this one friend, let's name her "bee", I would say she is avoidant, because there's this one time that we were just reviewing for an exam, we were doing like q&a with the other friend and I've asked bee if she wants to join, she then said she don't want to, we then respect her decision about that, then
a few minutes after she suddenly went quiet and being cold to us, and if other people approached her she would smile but when it comes to us she is like cold and poker face, we just let her like that because maybe she needs space or something. After a few hours she would come up to us and acts like nothing happened. Then there's this one time where I am chatting with someone and she asked me a question but I am still talking to the other person, I said wait I will answer her question first because she is the first one to ask me, after that I talked to bee what is she saying earlier, she then began to ignore me. After school she is still ignoring me, I said sorry I can't answer her question at that moment. I've become annoyed because she is talking to our other friend and kept ignoring me so I said whats the problem, she then acts like she don't care. Bruh I understand that people needs space and self time but I don't know what to do, this is always happening and all I do is understand and be patient with her. Sorry for the bad english, it's not my first language.