What should i do about my gf!?

im an 18 male and i hooke up with my girlfriend 3 days ago. she took me down to the park where her friends wer and they are all constantly getting stoned and drunk and end up coughing there insides out. she was complaining to me that i wasnt socializing muchwith her friends. i just cant find something interesting to talk about with these people and im concerned for my gf cause she also gets stoned with em and she does really stupid stuff like throw stuff at each other and fighting with the guys. i don't like hanging around these people and if i had the choice i wudnt let my gf either. i just came home cause im sick of them and i left her there and i bet theyll be doing stupid stuff and making fools out of themselves. what can i do? i really like her i dont want to risk losing her.