What to expect from my ex-girlfriend?

My ex-girlfriend and I broke up three months ago after five and the half years of relationship. We are both in our forties. She said she doesn’t love me anymore and that she doesn’t have any feelings for me for a longer period of time. Our relationship wasn’t perfect, but there were a lot of beautiful moments as well. We share a lot of happy and nice memories.
She had a lot of issues and I was always there for her to help her and support her, and moreover to love her in that moments. At the end of the relationship, I had issues and instead of getting the same support from her, she found another guy and dumped me. She forced me to move out from our mutual apartment.

During this last three months, those beautiful moments we had were all over my mind, more or less every day, and I feel regret that she has left me. But I manged to move on and worked a lot to improve myself and I made a progress.

But at the same time I kept calling her to come and visit me in my new apartment.

And then, last Friday she came to my apartment, we had a good time and we had sex. She stayed overnight. Yesterday she came again and we had a really good and passionate sex. But all the time she was telling me that she is satisfied with the new guy and that she is going to stay in the new relationship. When I asked her for the reason, she said that he treats her good, he is funny and that she is in a way taking advantage of him (something like he is paying for all the food). When I told her that I’m seeing someone else too, she started to cry and she said that she likes me the way I am now and that she feels regret I was not like that before when we were together. I told her that she can leave him and that we can try something again, but she categorically refused that. She said that she wants to be with him and maybe one day in the future, who knows, we are going to be together again, but not now. I found that statement very immature. As I said, we are both over 40 years old.

I’m also sure that she came to me and cheated on him, because she doesn’t care about him at all. But she said that is not the truth and that she fell in love with him.

I was quite fine, but now I feel distressed almost like three months ago. So this just brought me harm.

So why did she come to be with me? Does she really know what she wants? Who does she love?