What should I do? Girlfriend 21F, Me 23F, her BFF 20F

So I’ll try to keep it short , basically I lived with my girlfriend & her best friend for a month before it went to hell & mind you we split the bills in half but I pay my girlfriend part so I payed most of it.. rent is 1800 sum , her best friend paid like 600 & I paid the rest plus utilities & before that I lived in a house my mom gave me for a couple years rent free & I let her best friend live there for a good 6 months (rent free)before we moved & my mom didn’t allow it but I still snuck her in because I knew she had no where to go, well her best friend was gone for a couple nights & we ran out of soap so my girlfriend asked me to go in her best friend bathroom to get some soap, we forgot to put it back & then when her best friend came back a couple nights later she asked for it back which is no problem.(it was her bf soap) I will quote what she said. “Where is my soap, it’s not in here” (with a attitude) we said “oh sorry we took it when we ran out I’ll get it now” after that the friend got a attitude & starting saying “idk why this bitch is mad it’s my fucking soap” & calling me a bitch wen I didn’t get mad.. so I started arguing back & I was just wondering why she had such a big attitude when I’ve had roommates all the time & we always shared & never gave each other shit.. couple hours go by & we fight & she says some hurtful things like calling me fat for one knowing I have a insecurity of it.. & I promise I’m not keeping any details out because I want all the advice, I literally didn’t disrespect her once until she started calling me fat & a bitch but my girlfriend still talks & laughs with her best friend like nothing happened & I some how I just feel betrayed & my girlfriend knows it bother me so she puts there covo on mute , now im tryna just move on & let them be & forget but I stilll feel betrayed.. so what would you do?