I was assuming she talked to Rose; or, at least, the last person she had talked to in her call history.
I think at this point we almost have to decide/accept that the very last thing on Gabby's mind was ratting out Brian to her family on any abusive tendencies; thus they'd probably be the last people she called.
I don't think she called Rose. Rose was bothered GP didn't call her after that incident. And said when she last spoke to GP it was "early August" and they talked about getting together for Rose's birthday at Yellowstone.
Brian Laundrie was controlling, had 'episodes': Gabby Petito pal
I thought she called her mother but from what NP said it doesn't sound like she did.