Whose at fault?

Brief info Me 23M a average looking tall guy who used have great flirting skills (now dead inside) Her 22F a bright good looking very active girl A high ranked NCC cadet, a kathak dancer, gym/zumba trainer, a very very good liar/con

Hi recently i had a breakup, it was my first love and all the other experiences with her.... I was in my 1st year when i got to know a girl (later to be my ex) and got close to her and became bestest friends she started liking me after sometimes and accepted it but at first i didn't liked her but she never left me or moved away from me then after 2yrs I fell madly in love with her and i proposed her and she said yes she used to say that im his 1st bf ever and all.. For every thing... After dating for a while i grew suspicious of one of her friend and started collecting some leads and i talked to him after sometime and he told me that he dated her during covid period and had s*x with her too (she said to me that it was her 1st time with me for everything) then i confronted her and she accepted with so much rona dhona and all and i forgave her Then later the trust was broken but i still loved her Then one day i was going through her ig story archives and found out that she had dated her dance teacher who was like around 30(m) when she was in 10th 18(f) and boom i was shattered to pieces at that time she was in NCC camp after 10 days when she got back home i talked to her then she started her rr rona dhona and all and after sometime we broke up...And she told everyone that i used her invaded her private life and destroyed her college and social life by telling the truth and lies to everyone (jabki i never told any1 she told everyone then they asked me that did i do that then i told everyone the truth 😂)..