Background: 18 yo guy still in highschool who only recently discovered TRP. I met this girl a couple of months ago in my biology class and although in the beginning there was little to no attraction between us and I had almost no prior experience regarding women, 3 weeks ago I invited her to my place and we hooked up (just making out, no fucking or anything as I was still a virgin).

After one week of casual dating, she initiated the talk and I agreed to exclusivity. She's also 18 but used to only date older guys - as old as 25. She looks decent, but had a shit ton of red flags such as drinking, smoking, many orbiters, a fucked up dating history (drug addicts and dealers, djs, musicians etc) and of course heavy drug use that I decided to ignore. In the beginnig of the relationship everything was fine, great sexual tension, she seemed really obsessed with me and kept on saying to everyone that she loves me.

Without mentioning the trivial shit that she did that bothered me slightly, I'd like to talk about a few major events that led to the current situation.

First of all,she sent me screenshots of guys flirting with her that she didn't directly shut doen, yet decided to be ambigous to. Then there was there was something that confused me greatly. After only 10 or so days of dating, she told me that maybe we were moving too fast. We hadn't even had sex by then and I also found out that in the past she had at least one ONS with a friend. The first thing that really got me thinking was when one evening at about 1:30 AM while I was out of town we were chatting on skype and she told me that she had to go downstairs to see someone (she still lives with her parents). She just quit the chat and didn't message me until the next day, when she told me that it was her ex who she had met. She claims that they broke up on good terms because he had to leave the country for a month and that they remained good friends. Later, she explained that since we were about to take a trip to the beach in a few days, there was no other opportunity for them to talk and they had a lot of catching up to do. I didn't make a great deal of it at the time and proceeded with our plans for the upcoming trip. Yesterday we left for the beach, just the two of us and a tent. Although we had a lot of plans and she seemed very excited about it before, now she suddenly turned cold and distant. I wasn't really feeling it and wasn't enjoying the clubs and pubs that we visited and neither the people that we met and she told me that "I gave her bad vibes". Today, a couple of her guy friends visited us and she said that we should go with them to a nearby music festival. I didn't like the idea and would have rather spent time with her doing other things, so I told her that I wasn't really interested and that since we went there together, we should also spent time with eachother and enjoy ourselves. The shocking thing was that she just left with them and later messaged me informing me that we'll meet at the train station the next day. So she just left me alone in a place that I didn't really enjoy with absolutely no one to stay with and all of this without even trying to appear to give a fuck. After receiving advice from a few feiends, I decided to cut contact and return to my city where I am now spending the night at a friend.

Side note: We only had sex once in the three weeks that we have been together.

My question is: What's your take on this situation and the relationship in general? I still have feelings for her and would like to continue the relationship. My friend (the one who introduced me to TRP is sure that she is not only very disrespectful to me and in general bad relationship material ( I didn't vet her at all and she is my first), but also that she is cheating on me.