How can she find someone after how awful she treats people?

My ex recently got engaged 8 months after we broke up for good. Granted she's Mormon and it's not a surprise. But she's such a toxic, manipulative, and terrible person.
She led me on for years saying she wouldn't let the religious stuff get between us. My friends, my family, and even some of HER family have acknowledged how shitty of a person she was.
When we first dated, we were co-workers, and she dated me and another co-worker because she wanted to have 'fun'. Then hot mad when we both stopped asking her out.
She let me take her family to a baseball game and broke up with me that night.
Then she stalked my Facebook and kept asking sister how I was doing during the breakup.
She kept blaming me for the breakups when she couldn't make up her damn mind.
I have her absolutely everything I had in our time together to make the relationship work and everything and she threw it all in my face.
She even left at the peak of our relationship for a mission, pushed me out of her life and would only talk to me to convert me. She never replied until I ran into her much later and insists she did nothing wrong and I messed the relationship up.

How the hell has she found someone to marry so damn fast?
She dated 2 guys while we were broken up and stopped seeing her because she was crazy. Then she came back to me.
I know I was dumb to stay in the relationship.
How can she find someone after how awful she treats people?
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