My gf(21F) cheats on me (23M) with his bestfriend in early phase of our relationship

So here, me (23 M) in a relationship for 1.5 years with my gf (21 F), we met in a clg she was in 3rd year and i was in 4th year. She was extrovert and i was introvert. In starting our relationship goes pretty smooth, as they say butterflies in stomach. And after sometimes we exchanged our insta ids and being in love with each other.and she had mentioned that she had a bestfriend and they are only friends and no other intensions. I said okay, but i warned her that ki boys ladkiyo se kbhi sirf dost bnke nhi reh skte, and i had trust on her. But after sometimes mujhe thoda shak hua then i started to check her chats with best friend , fir mene dekha ki ye dono to bc couple vali reel share kr rhe h, and jab or detail m gya to pta chla ki pehle mere gf ka vo crush tha pr vo couple ke stage tk nhi jaa paye,. So in sab ke baad mene us se pucha ki tumne mujhe kyu nhi btaya, to usne bola ki tumhe bura lgta ye vo, and fir usne mujhse vola ki abhi vo bs friend h, m uski baat maan gya amd we continue our relationship, in sab ke baad vo bhut acchi gf bhi bni, she take care of me and loyal types, and fir in sabke kuch mahine baad her bestfriend blocks her and our story going smooth. But after 1 year when i was cheking his snap account, i found that in the starting of our relationship she kissed her bestfriend by visiting his home and after that i completely shattered and fir mene us se pucha to she was crying and saying tb m serious nhi thi ab m hu, and ab mera us se koi contact nhi h, jo ki abhi sach m nhi h, but she cheata me in starting of relationship and now she is loyal.

Baad m uske bestfriend ne us se contact krne ka try kita uske friends ke through, he try to manipulate her but usne contact krne sw mna kr dia, and unki friendship tutne se pehle vo usko emotionally blackmail krta tha ki vo breakup krle vrna unki friendship khtm ho jayege , pr usne aisa nhi kiya so pehle usne block kiya mere gf ko fir isne bhi kr dia

So what should i do, breakup or give her a chance?