The mother, from Preston, Lancashire, said: "I couldn't believe it. This morning I thought I'd check her Facebook profile and four messages appeared from this weird person.
"I just started replying to him pretending to be her. He said 'are you on your own' and 'go in the room and shut your door'.
"After a bit, I just told him I was her mum and said 'what are you doing?'
"He's deleted two of his accounts but I think he had at least three originally. I want to warn other children and their parents about this man."
In one of his first messages while Carberry was on the profile, the man wrote: "Do you promise to keep your mouth closed about what is said on here, staying in here only and you cannot tell anyone else okay?"
He then continued writing: "Are you in your bedroom on your own?"
After the shock of realising how easily predators can groom children via social media, Carberry went online to warn others against the man who was talking to her daughter.
When she started getting messages from other concerned mothers, she realised the alleged paedophile had been trying to contact young girls from across the northwest of England.
Carberry said: "After I posted the warning, other mothers have got in contact with the messages he has sent their daughters.
"I have got his real name now after posting his picture too.
"One woman claimed she reported him to the police a few weeks ago and they have obviously not done anything. It was the same man.
"Her daughter said something like 'I've got to go to school now' and he said 'no you don't, sit down'.
"On his 'about you' section, it said 'I am Jess, a 31-year-old transgender female and I only speak to girls'.
"I've spoken to my daughter about online safety but she's obviously accepted him.
'She has a friend called Jess so I wondered if she might have added him thinking it was her. I'm not sure.
"I've told her what's gone on. She hadn't even messaged him back though, which is good.
"I'm going to have to keep everything checked on social media from now on.
"It's just what I have got to do as a parent to make sure they're safe but it's a difficult thing when she's 13.
"With the comments I've received since posting online, I'd say he could have been talking to at least 100 children."
A spokesperson from Lancashire Police said: "We can confirm that a report has been made and we are investigating it."