I don't know

Is it a bad idea to be friends with your boyfriends ex who he cheated on you with? This girl was his first love, he won't admit but I know it. She dumped him, and kicked him out and found a new relationship soon after. He and I started dating and he cheated on me with her. She messaged me one day looking for him when he and I split for a few weeks. Not sure what happens with them exactly but they stopped communicating and he asked me back. I stupidity said yes. He's my first and I love him so much it hurts but I sometimes feel like I'm just floating in the middle of his and hers relationship. Today I saw that he and her are Fb friends again, after not being friends on Fb for months. She was liking his pictures. I don't understand what her problem is, she acts like me and her are such great friends and she's always sending me pictures of her and her boyfriend who she claims she loves and wants to marry but then she's randomly coming up in my relationship, either in his inbox or in his friend requests. Why are girls so disrespectful? Why do they think it's okay to but into someone else relationship and if she was my friend like she claims to be then why would she do this to me?