That other girl....

Hey, So im currently in a relationship which has been going just over 1 year, shes a fantastic gf and I feel lucky to have someone like her. But here lies my problem, before I met gf I was talking to this other girl and totally unexpectedly started to fall for her pretty bad. In spite of this she had just come out of a bad break up and had trust issues, she tried to end it with me many times but we both found it very difficult to not be in contact. After 4/5 months we eventually parted with her saying “I don’t know when or if ill every be ready”. I obviously devastated was kinda holding on for about 2 months after, hoping she may get back in contact with me. She didn’t. I just had to accept it wasn’t meant to be and I should just move on. From there I went out with a few girls and eventually ended up finding my current gf. However within the first couple of months of dating this girl, the previous one messaged me. Even though I found it very hard I pretended not to be interested anymore and carried on my relationship. Again though she messaged me a couple more times even after a whole year she was telling me she still thinks about me a lot. But I just didn’t entertain the conversation. So recently something really reminded me of her and I messaged her wondering how she was doing. We got talking and she revealed she had just got a new bf. I suggested maybe we should go for a coffee and catch up. However she said “Im sorry I cant, I wouldnt be there just for a chat, its not fair on my bf”. After hiding my feelings from her, I did break I told her how I still felt. I suggested maybe we should just give it a go if our feelings have survived this long. But she said she was happy atm and would be foolish to throw that away. I respected her decision and left it at that. I have told my gf that I still have feelings for this other girl because I hated hiding this from her. But I pretend not let it affect me that much. I feel like I buried my feelings because I felt like it was unfair on my gf to act on them. Now talking to the other girl it seems like shes doing the same thing with her bf because she thinks its unfair too. But really indirectly we have been unfair going into relationships with unresolved underlying feelings for another person. What is the best course of action, I cannot decide. Any advice?