What is this girls intentions with my boyfriend and what do i do?

Hello! I am 19 and I have a boyfriend of about 4 months now. He has this friend named Tina she is very attractive and they have been friends with my boyfriend for a long time. Tina does not live in the same city as my boyfriend and I so they do not hang out very much. I was happy to be meeting such a good friend of my boyfriend's until she showed up to hang out and mostly ignored me and started playing with my boyfriends hair then continued to flirt with him and tell him she is going to sit on his lap. While this is happening I am sitting about 6ft away from them. My boy friend apologized later saying she didn’t know better because of her troubled past... this was a while back. My boyfriend and his friends have assured me they are just friends but I do not know her intentions or if she is trying to get to me. Now more recently my bf said we should be friends but I have a problem with how disrespectful she was to me when we first met I also dislike the comments she makes his facebook things like "I love you" and " we need to play soon". “Play” I guess is her way of saying hang out... I want to be mature about this situation but she is starting to get on my last nerve. Thanks so much for reading all of this!