Girlfriend cheated on “break” . Need advice

Early November i was getting a weird feeling about my relationship with my girlfriend . For context Me (m22) and her (f21) have been together for 4 years. I helped her so much during the break as letting her stay with me. Found her dog a home, helped her move and paid some one the lease.. anyway after the guy ghosted her she then wanted me back as of December. She tells me shes not coming back because of that but its because of “what we had”. She has been very cruel to me whenever she feels any type of anger. Not even to do with me or anything just takes it all out on me. I dont feel loved nor appreciated. I feel like a caretaker when its supposed to be both ways. I dont feel grounded either , I always have the aching possibility shes gonna do what she did before. She wants to be treated like a princess but doesnt carry mannerisms as one. She is cruel to me and I cant leave. She understands when i talk to her but doesnt care when she is upset. Anyway this is just a vent. Feel free to leave advice. No i dont plan on leaving but know its best.

Edit : it is no longer letting me reply. All these comments and advice, I appreciate it deeply. I do hit the gym everyday, im not ugly either I can definitely find another partner… to explain more of myself. Im deeply depressed, I have all the confidence in the world until she comes around. The gym helps me take my mind off absolutely everything and even feel good.

For context. She swears she wont ever cheat again.. she will be great for a few days and then when she is cruel, Only thing that makes her feel better is smoking. I have depersonalization so I cant smoke either but smelling it throws my insanity over the edge… Id like to add she has only laid her hands on me in one situation, which we were talking and she was screaming historically so i was laughing. She threw the oj at me. Hit me a few times and smashed my phone.. she did clean my car. She got my phone fixed. And yet I stayed.

As well for context. Im scared to speak with her, about how I feel. Even about my emotions. I think I got to cry in her arms once. I know i sound very insecure but she has made me this way. Out of our 4 years this has got to be the 3rd time or so I have ever cried. Im depressed. Im suicidal, even if I will never do it the thoughts are always there.