It’s done… life is over… now what???

This past week has been rough. Me and my gf of 8 months broke up while she was in college. I'm 21 she's 18, but it seemed like we had the world to ourselves real soon. She'd always tell me how I want you and no one else and I'm never breaking up with you and I'm never going to cheat on you, even when I fear it. Well last week it just came out of the blue. She texted me saying she was losing feelings and I wanted a way to fix it because, yes, I have to admit, it was either her or I was done with life cause I couldn't go through heartbreak anymore. But later that night I started getting a gut feeling that another person was involved. So I asked her to tell the truth so I could be at peace. She said she had feelings but didn't do anything. Basically admitting that she emotionally cheated. Then turns out not even a day or so later she's already onto that new guy. Pretty much a rebound, and I just haven't been like this for awhile. I feel like I just lost all my happiness for a long time and I'll be damned if she ever comes back. Like my friends say it might happen, but I’ll honestly be praying for a miracle. Like we want to not be strangers and we're both still hurt over this. Today I went over to her house while she was away in college to get the remaining of my stuff. Me and her mom shared a long good cry as soon as I walked in the door. Then later I texted her saying I left, we can be cool, and we added each other back on socials. But I know for a fact it’s not gonna be the same when we’re just friends and nothing might not even happen. Overall I just don't know what to do and I feel like giving up...