Honestly I love the idea of hot girl summer, and I agree that it's a great aesthetic to aspire to once school's out! As long as you don't treat it as more than an aesthetic, you're in for a good, fulfilling time.
I'd say that a glow-up would target your physical, emotional, and intellectual well-being. So maybe you could work on your fitness, have fun with sports (do you play any sports?), eat food that you like, go places (esp. dancing, shopping, picnicking, swimming, makeovers, all that fun stuff!) watch great movies and read cool books, etc. You've had a pretty rough few months, and so it's great that you're looking forward to a summer of fun and self-care. It would also be great to make new friends at camp, or be reunited with old ones.
As for a short and sweet summer romance: while it's completely dependent on your emotional state at the time and the people you meet, I will say that the rebound advice you received seems a bit suspicious, especially when the breakup has been as distressing as you said it was in your previous posts. Quoting from an article
we have on here:-
Give yourself time to be single after a relationship. Sure, now and then we rebound, or a new relationship just happens. Sometimes, a new relationship may even be why the old one ended. But most of us need time to grieve and reflect after a breakup, even just to remember and reclaim who we are all by ourselves, and as ourselves, not as someone's boyfriend or girlfriend. If we don’t have time to feel our feelings, as well as time to learn the lessons of our last relationships and the breakup, our next one might not be any better than the last. Too, after a breakup, we so often feel so lonely, having been used to having a partner, that relationship choices made hot on the heels of a breakup don’t tend to be our best. When we're feeling desperate to get validated, or to be with anyone so we don't have to be alone, we'll usually wind up with people who are way less than awesome.
Not all of that advice is relevant to you: you haven't said that you're feeling lonely, and you're also not looking to be in a serious relationship. So like I said, context is key. Say the person you decide to have this summer fling with is OK with being a rebound, and say you're not hinging your hot girl summer on having a romantic and sexual time (to my understanding, "hot girl summer" is mostly divorced from that genre of human activity, it's more "me and the girls and the allure we hold", which I think is super healthy, because for the rest of the year, everyone is 24/7 shoving romance and sex down your throat). If that's the case throughout, it's entirely possible that the summer fling ends up being very healthy, very sexy, and very fun! Does that make sense?