Have you ever had this happen to you

So about two years ago I met this girl , she approached me sitting outside my group therapy classes building one day she asked me if I was there doing groups , I said yes I am , she asked me what groups I do and I told her , she wanted to know if I could suggest some groups for her and I told her well that all depends on what issues you have going on in your life that you want to get help with she began to tell me about some of her issues , I won't mention them here but I did end up telling her about some if the classes that I personally take , we talked for about 20 minutes then we exchanged phone numbers and kept in contact and hung out for sometime after that , I really began to like her a lot I even started to fall for her , and we were even intimate a few times , the bad part is she eventually (after three months) came to me and told me she just wanted to be friends because she has a boyfriend , I felt like she played me and I felt really used and taken advantage of and lied to , I was broken hearted and I felt betrayed. I have tried to suppress my feelings for her and we have become friends although for a long time my feelings for her were still evident but as I got to know her ad my friend my feelings got less and less and I no longer have any loving feelings for her anymore.