Search Results: staying friends with ex

I've been in a relationship with this girl, Amy, for the last 3 years, a month ago we moved in together, we love each other.
A week ago, i wanted to surprise her, so i took a flight to her hometown to buy the salt candies she used to eat when she used to live with her parents cause it reminded of her childhood, after that, i bought some flowers and took her to a movie and cooked a meal for her.
Everything was going great, but when i gave her the salt candies, she started crying, telling me "she doesn't deserve me"
Then she told me she kissed her ex in her office 2 days ago.
I died inside that day, i ran away from what it used to be our home.
She kept calling, texting, showing up at places where I'm staying, asking me to let her explain herself. Her explanation was that she made a mistake, she used to love him, but she loves me now. A part of me wants to trust her, but how can i?
It's been 10 days, i wanted to marry her, but now I don't even want to see her. I don't have any friends, maybe that's why I'm here.

This question is motivated by a small discussion I was having on another site. It has always seemed to be women to me who can't let an old partner go, even though they might talk a lot of big talk about "being done" and moving on, they will still watch an ex on social media or even ask their friends and family about him. It seems like in the beginning they will let go completely and it might even hurt the guy, but later on they're still thinking about him or watching him on social media, even years later when he's in a totally new relationship or absolutely married. And of course, you have a lot of women who can't seem to move on from guys who don't respect or treat them well, and they'll try to hold on to him even when he keeps pushing her away.

I too recently had a family member tell me that one of my exes was asking about me - after all this time! And she was the one who ended things. I have zero interest in reconnecting with her whatsoever, as I have also grown a lot more as a person and a man since that relationship. So I find no value in re-uniting with her.

I am not saying that men never run back to an ex or can't let them go, they do exist. I'm just saying it seems like a bigger thing with women. What do you guys think?