Here's my thing. Right now i'm kind of in the situation you were in 4 years ago, so I completely understand. I may be speaking with a narrow minded view here and if so I apologize in advance, BUT in my situation the girl and I became friends at first. Then those feelings developed into a more than friend feelings on both sides. We got extremely close in a romantic way and then she kind of pulled back saying she wanted us to be best friends. At first I felt like "best friends" was better than not being friends at all. But even as a "best friend" my romantic feelings for her were still there. Eventually I realized that it was just tearing me up inside to have her as a "best friend" when what I really wanted was a gf. She called me selfish for that but in all this time i've had to myself lately, I think she's the selfish one for expecting me to be ok with being the close friend while knowing I'm in love with her, while she has a bf. I don't really know what to say given how long ago it was that you two broke up, but I still think that even if you continue to talk to her it should be at arms length. You don't want to set yourself up to have your heart broken again.
Be careful with your heart, because when someone seems too good to be true, they usually are.