What are you freaking out about?
For those situations I've actually learned a lesson about those. I usually carry a spare old smartphone with me (usually people don't do this but... having no phone in remote-ish Thailand kinda sucked). As for the passport, always carry a photocopy of it with you. and as for losing your money, I always leave $50-$100 in cash hidden away in a separate bag. I also always carry 3 credit cards with me. One with my passport, one in my wallet, and one in my bag.
You'll be fine. I'm a mean looking 6', 230 lb, linebacker-looking tanned/dark dude, and i was able to make tons of friends when I stayed at hostels/partied. You're a girl, you'll have absolutely no problem making friends.
Have you looked up Female-Only dorms? This was the biggest advice I've heard from women i've met while abroad... that they were able to have a safe space to meet other solo/grouped women. You should look into that.
I don't have much planned other than dates and cities and a couple of lodging options I needed to pre-book far in advance.
On my previous 2-month Eurotrip, I literally bought my flight 10 days before leaving. Aside from knowing what time my flight was, I had ZERO plans, nada. I flew into Heathrow and literally opened google to find a hostel to stay at for the night. A couple days later, I woke up that morning and thought "meh, i wanna be on a beach in france instead", and got a $80 flight and was on a French beach later that day. Europe is easy. No worries.