Should I add my boyfriend's friend that's a female on facebook?

[Giraffe♡]

So I sound like a preteen going through a drama queen stage but hear me out. This was awhile ago May of 2013 and it still bothers me. I am 19 years old and my boyfriend is 22. (I will be 20 and he will be 23 soon). He has a friend that he is close to or was anyway. They don't talk as much anymore. She has a boyfriend and of course my boyfriend is with me. This friend of his asked him to go to breakfast with her at 6 AM in the morning. My boyfriend told me about it and then he asked, "Why didn't she ask her boyfriend instead of me?" Jealousy of course fired up inside me. In a previous relationship, my ex emotionally cheated on me with a girl he was close to so he broke up with me. Memories flooded back of that time when I as hurt so, could you blame me being jealous? Anyhow, I only spoke to this girl once and when i met her she gave me a sneer. That was way back when me and my boyfriend were still a fairly new couple (Estimate maybe a month or two in). Anyway, I do not care as much anymore about her and I wonder if I should still add her. I mean, i can't say i don't fully care because I do. That time still is in my head wondering if she secretly likes my boyfriend even though she has her own boyfriend. Should I add her or just forget about it?

I don't have any of my boyfriends friends on facebook because they do not have a facebook, and she seems to have one. I dunno.