How long did your hope ultimately last for before you let it go?
Our relationship lasted about 1.5 years, so I'd say I waffled in that time from thinking we could at least be long distance friends, to believing (again!) that we were going to build a life together.
but then i think, so what if there is? so what if they break up, and she comes back? She left me. She replaced me with multiple people over the last year. She doesn't check on me, or wonder what I am up to. It's like I never existed, so why the hell would I want a heartless person like that back?
These are really good questions, Indifferent. Focus on your values—who you are and what you stand for in life—and take steps to live by them. That may not include someone who cuts you off like that (and also, you could examine the ways you "don't exist" to
yourself when you are overly focused on her).
I know I've gotta live my life. I come here all the time saying that, then end up checking her crap.
It's so understandable and human. Be gentle with yourself. Habits and coping strategies take time and effort to transform. It's not comfortable, it can take longer than we expect, and it certainly can not happen in the way we think. Awareness is a huge step forward, though, so you've already won half the battle.

I feel like a part of me will ALWAYS want her
Maybe, but I'd bet money that you will feel differently in time. It is amazing how feelings can change during this process. After my breakup, I felt like I was an emotional wreck and felt deeply apathetic about life (depressed). Today I feel joy and gratitude again, my life has changed for the better, and I feel optimistic about the future, even as I enjoy the present.
Things really do get better, Indifferent. Keep working on your detachment. Focus on your wellbeing with big doses of compassion. We're here for you.
heartandwhole