<human>: Can you condense the text into a few key points?

Her best friend is the one that set this up but my girlfriend asked me about it. I've never met her best friend, her best friends boyfriend or the other couple although my girlfriend doesn't know the other couple either.

She said that I didn't have to come and seeing as how terrible I am with people and that I don't know them I said no sorry. Then she says ,"yayyy fifth wheeling". I apologized more but I feel terrible about this. I think I should go, but it could go terribly. I feel like a good boyfriend would say yes. I guess I'm asking is saying no okay? Is this the right decision? Would you go on a triple date with people you don't know? 

Advice?
<bot>: Girlfriend asked if I wanted to go on a triple date with people I've never met. I said no and feel terrible.