Hey deek, 27 year old actively dating woman here. So basically your target demo.
About a year and a half ago, I went through something similar. Super intense relationship, I was head over heels, thought he was too, and he dumped me out of the blue. Told me he "just wanted to be single right now" and had a new girlfriend about a 6 weeks later. We dated about 3 months and I was heartbroken for ... maybe 4 or 5 months after that. It was horrendous and awful and I felt like an idiot for being as sad as I was, but it was incredibly painful.
At first, I was way too focused on "getting him back." Once I saw him with the new girl, I was at least able to let that go, which helped a lot.
I would note that I eventually (like only a few months ago) found out that he had cheated on me multiple times right before ending things, and I've heard a few other things through the grapevine that make me feel like I dodged a bullet there.
Honestly, though? I still don't want to be around him. I still don't go to parties if I know he'll be there. I still have a little too much glee when I hear about things not going great for him. I don't wish him pain, but I don't necessarily wish him unending happiness. He hurt me BAD, and while I don't feel sick to my stomach thinking about him anymore (and haven't for a long long time), we're not friends. Could we be, someday? Maybe. We have mutual friends, I'm sure I'll run into him eventually. But I'm not going to seek him out.
I finally deleted him off Facebook 6 months after we broke up. I recommend you do it much sooner. Like now. If you eventually reconnect, any sane person will understand why you deleted them. I've done it with other exes in the past and re-added them later once we were good. No one took it badly.
I met some really nice people through that ex, and did end up maintaining friendships with them. That mostly happened because of shared hobbies (which he conveniently quit after the relationship ended, nicest thing he ever did). However, if you have people like that I'd make an effort to reach out to them to hang out and then DO NOT MENTION HER. Talk to them like normal pals, not to get scraps on information about her. This is only worth it if these are people that you really want to keep in your life for their own sake. It only was worth it for me because I had just recently moved and really needed friends regardless.
Don't reach out to her. You'll feel pathetic about it and regret it later. That amount of vulnerability post-berakup, particularly in a relatively short and casual relationship, feels really embarassing later on. I have a different ex who I was super vulnerable with as things were ending, and it's prevented me from being able to be friends with him at all - I just hate knowing that he's seen me at my absolute worst, a version of me that I really don't like.
Things that help? Time, mostly. Journaling. Hanging with family (if you're close to them) or going to visit an out of town friend. Intentionally building new relationships (friendships - if I try to date too fast, I just find myself crying on the way home because "They're not _____," and it's unfair to someone who might be awesome in their own right). Active and social hobbies (mine is swing dancing, a great way to meet lots of new people). Time.
After that terrible breakup, I wrote the numbers 1-100 on a piece of notebook paper. Every time I successfully went a day without contacting him, I wrote NC next to that number. By the time I got to 70 or so, I'd forgotten that it was a thing I was supposed to think about, he had just faded from my mind and my heart and wasn't a daily consideration anymore.
Best of luck. This is hard.