About 6 months ago I helped my girlfriend's family move out of their home into a different home because there is no other man to help with the physical labor aspects. For about 5 hours I am the only one picking up boxes and moving them into the loading truck, meanwhile my girlfriend's sister would randomly pop out and say, "I'm sick of seeing your face" (I was sweating) "You're a lazy ass bum, get to work or go home" (I'm the only one working remember) and countless other verbal assaults. I ignored all the verbal assaults and did my best to not yell back out of respect for my girlfriend and her mother because this was the first time I met/saw her sister and I was working on making a good impression by working hard for their family. Finally, at the last verbal assault from her sister, I couldn't hold my tongue anymore and sweared and yelled other obscenities back at her sister. Little to my knowledge at the time my girlfriend and her mother were in ear shot and heard everything I said. I still do not forgive my girlfriends sister for the complete disrespect I was treated with when I was helping, or do I ever plan on saying sorry. Now my girlfriend says her sister wants to give me a second chance (wtf for??) and wants to go out on a double date with her boyfriend and my girlfriend and I. I told my girlfriend that I am sorry and would really not like to be around her sister at all because I am someone who never forgives or forgets the past. Am I wrong for not wanting to go out and see her sister? Am I wrong for not forgetting the past and trying to stabilize the tensions? What should I do or say to my girlfriend? Why should I come out for a "second chance" when I did not start the tensions? Any help guys/gals?