Have you actually asked your g/f whether what her 'friend' said is true?
I tend not to put much faith in the whole 'he said that she said that she said that your g/f said this to him' scenario!
If someone has a bone to pick with me they might as well simply talk to me face to face rather than using the verbal post office! Messages sent via the verbal post office are often garbled, changed entirely, late or never arrive! It's best to deliver the message myself and save myself the grief and frustration of relying on someone else.
Good luck. I hope your confusion lifts soon.
There are as many ways to do polyamory as there are people practicing it!