Sharing Our Innermost Thoughts

I got engaged but my ex is telling me it could have worked out between us

Met my ex in college. She was in a long distance relationship at that time which didn’t worked out and we kind of got together. I loved her and hoped for the best.
First 6 months she was already talking to some other guy, never turned down his advances. Then went into a relationship with another, which didn’t last long. Came back to me and I still accepted her. Things continued with the new guy for a while and I finally confronted her and we decided to part ways. For some reason still stayed in touch(common group of friends).
Was always there to help her,even shared an apartment with her and shared rent when her best friend left her after 2 months living with her.

I was hopeful that things could work until I saw her texts on snapchat. She was again in a relationship with another guy from work. Turned out the same guy who received her at the airport when she came back from home, and went to his place for the night.
Still looked the other way for some reason and last year asked her to make a decision as I am getting older, she said “ I don’t see you as a partner, I don’t have feelings for you, I have cheated on you”. Shit broke me finally and I decided to move on. Meanwhile she got into relationship with some other guy from work, practically lived at his place and time to time told me that we were never meant to be,she never had feelings for me. She broke up with him too.

I Worked on myself, lifted my standards and met someone. We hit it off and got engaged last year. Ex got to know and is telling me if I could have waited more for her she could have married me because of how broken she is she doesn’t care who she is with and she always fried to work it out with me.

I am hell lot of confused what to do now. What do i tell my ex to do? Should i have waited for her to finally come to her senses?