18M and 18F in an LDR, how do i fix my trust issues?, boundaries, college life etc, questions related to these needs answering

Hey all 18M here
Me and my gf(18F) started dating in 2023 while we were both in 11th grade, fell in love real hard and she was perfect, dated all the way through 12th and now she has got into a college and im taking a year off to better prepare for my college entrances. Around last september while checking her instagram i saw a post of hers with her new college friends. She has 3 guy friends and im like kinda fine with it but at the same time kinda scared about it too . Ive had some trauma in the past about cheating where my own father cheated on my mother during my 12th grade and she cried to me a lot so i have a lot of trauma related to cheating
that trauma is now being transferred to her so since she has those 3 guy friends it makes me scared
so one day in september this year i was looking at her posts and came across one where she was sitting with her whole friend group(both guys and girls) and she had her hand on another guys arm(the guy is one of those 3 guy friends i mentioned above) like holding his shirt or smth and it just threw me off like i felt so visibly disgusted seeing it cuz i just hate it when my girl touches other guys it just makes me want to vomit because i see her as pure in mind and body and such things makes me feel like shes losing her purity.
I talked to her about it she apologised and we moved on from it
Then in september of this year i was again looking at her posts when i came across another post of hers, actually 4 posts just pics in the same pose but 4 different pics with her in her friend group, but in all 4 of these pics she has her hand on the shoulder like in a suspicious manner of another guy(again another of the 3 friends) and when i saw it i literally felt so visibly disgusted just seeing that . i confronted her about it and asked her "Why do you keep doing the things that hurt me ive already told you this hurts me so much yet you still do it" she said she did it unknowingly but i dont know how you put your hand on someones shoulder like that , that too in 4 different pictures, unknowingly.
I gave her the ultimatum, either stop doing this , or i end this now. i told her that if i ever were to find out that she did something like this where she touches another guy for no reason, i would end the relationship then and there , no questions asked. She started crying and said shell try her best not to do it . But i dont understand , what is there to TRY? all i asked her to do was to not touch other guys like shes talking as if her body has this neccesary condition that she has to touch other guys during pictures and she has to intentionally TRY to not do that. Like i hated how she used the word try cuz it didnt make any sense.
I dont want to leave her but her repeatedly doing such things just makes me lose interest in her day by day, ive given her the ultimatum and if she does it again, this ends
Now my issue is whenever i think of how she did it a second time despite me having told her the first time how much i hate, it just makes me so mad that she would even consider doing it a second time like why all i asked her to do was keep her hands to herself its literally the most simple request ever cuz you can never know how the other guy might take her seemingly friendly action
Im just overthinking and confused and just disgusted about her behaviour
please, i need advice on what to do to restore my mental health cuz im on the verge of losing it all cuz of these problems