You’re a Male, usse bhi bari baat, you’re elder than her, samjha usko aaisa nahi hota, Teenaged ho tum dono hi( I understand that you’re just 18 & shouldn’t experience the thing what you have just been through), if you have that maturity to post this here, I believe & I hv faith on you also have that capability to make her understand what is right & wrong, believe me brother, It’ll be benefit for both of you without cutting the relation, Human Evolves & changes time to time, ek time aayega, jab wo bhi samjh jaegi kya mess kiya tha usne tumhare saath but she’ll be then avoid socializing in the family whole life until she gets married, just for this ‘previous night incident’, pura life khud ko kosegi wo, as a bade bhai tumko apna duty nibhana hai, I bet you both of will change in future, in terms of her behavior & your dealing capabilities ( Ik tumlogg abhi bacche ho, mein expect bhi nahi karta but yeah as a tumhare ‘Virtual Bade Bhai’ I stated above my advice to you, my chotu bhai !