Why were these people so confident about her?

I dated this girl for 4 and a half years and we had an amazing relationship. But she was a Mormon and decided to go on a mission and despite all those years together, she started treating me different. She eventually broke up with me, because I refused to convert.
During her time away, I had 3 Mormon women I knew because of her, and my friend who was married to a Mormon all say. That once she was home for a while, she will change her mind and reach back out to me and we'd get back together. Especially the Mormon people were very confident about that. Surprisingly.
But she came home and it's been 7 months, and I know she's seeing someone and I'm positive they are engaged already and I'm just shocked.
I went through her mission and her time back thinking I'd get the love of my life back, but it seems I've lost her.
Why were these people so confident she was going to come back?
Why were these people so confident about her?
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