My gfs best friend tried to kiss her, not sure what to do...?

so while at a party without me (we usually dont go to parties without each other because of things like this) my girlfriend got reaaaaaaally drunk and smoked some pot. The party was at her best friends house and i was ok with her going because there werent going to be any guys there. so she was in the garage with her friend. They were leaning on the wall and her friend moved her face really close to my gf and said "why arent we making out" my gf got really nervous and just said "what" and walked away. she called me immediately and we were on the phone for an hour. i live out of town and had work that night so i couldnt go get her. According to my gf nothing else happened that night and neither of them have talked about it. They are best friends and my gf goes to this girls house once a week to smoke... just them. I trust my gf... just not this girl.. and no before any guy says "WTF THATS HOT!!" no its not, not when you really care about this person... and not when you dated two other people who cheated on you with another girl... so what should i do.. i txted my gf saying she needs to tell her friend that thats not ok and she needs to respect the fact that 1) my gf isnt gay or interested in her and 2) shes taken by me and we love each.. the only problem is my gf wont say anything because she doesnt want to "rock the boat" and is hoping her friend just doesnt rememeber... so what should i do? ive been through this twice already and the familiar feeling makes me sick to m stomach