Should I have not introduced myself to my boyfriend's ex girlfriend?

[Christina]

My bf and I went to the movies with my family. I was in front of him and didnt notice that he got approached by someone. I thought it was just a friend he saw but it was hi ex girlfriend. They were saying hi, and I decided to go up to her to introduce myself, since my boyfriend was looking for me but couldnt find me.
Here's the catch. My boyfriend and I started going out when they were still together. I know, it was wrong. But we fell in love and he broke up with her. She really wanted him back, but now is over him. This was one year ago, and she hasn't seen him since then. So we bumped into her, and I humbly have been wanting to meet her. I finally had my chance to meet her, and I did. But when I approached her, she was obviously very VERY uncomfortable. She gave me a smile that said "Dont you dare shake my hand" but I just kept smiling and introduced myself. I think she was taken aback by the fact that I was so cheery and willing to be friendly to her. I dont know, did I do the wrong thing by introducing myself? The only thing she told me was "I've heard alot about you" awkward smile. thats it.