Need some Genuine Advice ... My brain is Cooked.... Is SHE cheating or wot!!

I am 22M and in a relationship with this women 21F and its been more than 3 years we are in a relationship . She was toxic when i was in college as she used to be at her home as she was prepping for some exams and we used to have fights when i used to go out with MALE friends like after colleeg or used to stay in college a little too much or in some cases when in a group of 12-13 friends (out of which 2-3 are girls) she used to say no to me for going and all that and i basically supressed myself from doing any things at college which were normal like staying a little more in college with friends and stuff like that and she used to fight with me for like 15-20 days in a month on topics like these

Now she took admission in an college about 1-1.5 months ago and she agreed and apologised as she now understands these things are like a part of college life and accepted that he behaviour was shity and toxic. I agreed ki its okay , jo hua just leave and move on coz i feel so bad after this and i cant change that and OBV i dont decide to to fights on all those topics as i know how it feels

Now she as a senior friend and she go out with him in his card (only my girl and that guy , she asked me that can i go with him ) and i said sure but remember u are in a relationship and be in your limits , now that guy used to flirt with her and she used to say dumb replies like "bhagjaoo (with laphing emoji)" and i asked he please ask him to be in his limits and you are commited as well but she made sure that she will never CHEAT on me in any CASE and she has already told that guy that she is in a relationship and that guy has also said her "ki i know tu relationship mei hai and mei teri boundary ki respect kerunga" (that i respect that u are in a relationship and i will respect your boundary and i will be in my limits) and they BOTH went out for a drive after college and had beer in his car (i got to know about the beer later) then few days later then went out again and its been only 1.5 month and they went out like this 6 times till now and i have fought with her regarding this twice and both the times she said that i will take care , i know my limits , he aslo said that i will not do but still he suedd to flirt and she used to reply him with same shit and she said to me that "i have asked him not to flirt but he says thats its not my problem that u are not single , i will pull ur leg" now idk pulling leg and flirting is same thing according to her

now 5 days back she met him in his card , they drank beer and she got a little high by the bber and said i ma sorry i got attracted to him now and all that stuff when i asked her to show the chat and i like a very good bf said "no worries , if u are feeling that way , take a step back and lets not stretch this things and fight over it coz i genuinely love you"

now 2 days back , she was coming back from the college and the saame guy approachhed and asked her that i will drop and you and we will go on a little drive or something and she said yes knowing that i am little insecure and she also admitted that if the case was opposite like if i would have asked her that i wanna go out with a girl in a car , she said no that i will not be okay and then she met this guy 6 times and she didnt told me that i am going out with this guy after the college and i got to know about it later when i msged her where are you as she usually msgs me after leaving the college , she said i am with this guy and i wasted her to come back and later i asked her to show me the chat and she said no sorry i cheated on you

Now again as a good bf , i tried to make the things calm and her as well and she didnt show the chat after that too and yesterday she confessed that the guy kissed her in the car and she didnt do anything as she was numb , then i asked for the chat , again she denied even after all this

I said i will forgive you if u will give me ur snap and let me msg that guy from your account saying that why did u kissed me knowing that i have a bf but she said NO and i wanted to do this coz she was defending this guy from over a month saying that he respects me and my bou dary and he knows that i have a bf and she was looking so desperate to go out in his car which obv made me doubt them and there were certain few instances where i asked her something about this and asked her to show and denied and gave so dumb reasons that made me obv

now yesterday she made a lot of drama and said i will not block him , i will gost him in few months , i have to face him in clg , i was like dude , there are tens of thousaands of students , why are u soo like , and why do u have to face him after all this and she still didnt showed me that chat , then she showed me some msgs and obv he was flirting with her and she was givng him like so dumb msgs that were obv no where asking him to stop , it was like he is flirting and she is enjoying and saying haha

and there are tens of other things that happened which really hurt me and i was observing that if she will understand that she is in a relationship and has a partner which is hurt and if she was in my place she would be soo fucked up , all those instances were so shady and full of doubts and dumb illogical reasons

now today early morning , obv i wasnt able to sleep after this shit , she msged me that i didnt kissed him and i was just checking if u would be n all those things , i was like dude , i am in middle of some examinations and i am studying 10-12 hours a day to crack an exam and get a good career for US and in middle of that u think this is funny

I asked her to make me believe somehow that she didnt kissed or watever and she said its ur choice now , i was like dude its ur choice to make ur partner comfortable and clear about things and i saw some snaps of her with that guy that she sent to her friend and not me OBV and there are certain other things like this and i am literally fucked
3 year relationship and now this , i never expected this from her and the whole one month she said 2 things (1) i will never cheat on you , i know my limits , he dont listen to me and flirts with me and she was not stepping back as well (2) he told me that he doesnt have any bad intentions with me , and if he would have before , he would have said earlier .......... to this point

And today she is going to her college with her friend instead of sitting with me clearing this and just doing it over calll with attitude like hasnt done anything and she has courtesy to ask me "What have I done?" after doing this mess

I asked her to delay ur chilling day with ur friend for 2 hours or just 1 hour and clear things still saying bullshit reasons like u dont have enough time to spare to save ur relationship, i am genuinely heart broken

Please suggest what should i do?