Thanks for the replies. I see everyone here is alluding to the fact that I'm better off without her, and I have to say I agree. I've been framing the loss of this relationship as something sad for me, and I've been wallowing in self pity. I did fall in love for the chemistry, for what she said, and for who she was at the beginning. I kept trying and trying to get us back there when she started acting out, but that was futile because she was showing me the real person.
I read something that someone who does not respect me, is not loyal, and cheats does not love me at all. Love is supposed to make it really hard to cheat. I mean, I never once fathomed cheating on her while we were together. She was my world. But she went out and cheated on me. I didn't really intend to leave her forever--just postpone the wedding for 90 days while she sobered up. When I left, I couldn't even think of anyone else but her. It took her mere days to start hunting. If she really loved me, her actions would have matched her words. Truly, it seems that she only ever loved herself. Love in our relationship was just about me meeting her needs. When I didn't want to do that anymore, I was cast aside without a thought.
It doesn't make sense for me to keep mourning the loss of a person who couldn't love me to begin with. I'm done seeing this as a tragedy. Not getting stuck with someone that didn't love me is the best outcome I could have hoped for. My love was never going to be reciprocated in the first place. I'll use this experience to become a better person. Thanks for listening.