The 42-year-old from Nottinghamshire is speaking out after Jordan Richards, formerly of Walton Street in Long Eaton, was jailed for two years for rape and sexual activity with a child.
The now 21-year-old had pleaded guilty to rape and not guilty to the other charge of sexual activity with a child but was convicted by a jury following a trial in February.
On two separate occasions in 2013, Richards befriended two young girls aged 12 and 13 on Facebook and after some months of messaging arranged to meet up with them which is when the sexual activity took place.
The mother of the girl who was raped now wants to raise awareness of what happened to her daughter.
She said: "I didn't have any suspicions that my girl was up to anything out of the ordinary online, she would chat to boys but everything seemed quite child-like and innocent, she didn't seem secretive about it at all."
During the trial the court heard how Richards had claimed that he thought the 13-year-old girl was older but the messages read out showed that he was aware of her true age.
The court was also told how he had sent suggestive and flattering Facebook messages to the girls.
The mother of the 12-year-old said when she found out the extent of what had happened to her daughter she was fuming.
She said: "To think that he had taken our innocent little girl, taken advantage of her naivety and age with the messages he sent then arranged to meet up and raped her is absolutely disgusting.
"She was obviously going to look up to him because he was an older boy, she didn't know what he had in mind, he should have known better."
Richards will now have to sign the Sex Offender Register for 10 years and was also given a Sexual Harm Prevention Order which limits his internet activity and contact with girls under the age of 16.
These include having unsupervised contact with a girl under 16, using the internet to contact a girl under 16 and deleting internet history.
The mum said the family has been through a lot over the past four years but this makes it all worthwhile.
"I'm glad that Richards received a custodial sentence in the first instance because hopefully that'll make him realise the seriousness of what he's done, but the fact that he's got these prohibitions against him means that when he does come out of jail, he won't be able to target other girls in this way," she added.
Giving advice to other parents, the mum said: "We knew something was seriously wrong because our girl's behaviour suddenly deteriorated, but by that point it was too late.
"We can't prevent our children from going online in this age but we've got to encourage them to speak to us and come to us if they do receive something out of the ordinary.
"I think most of the time they feel embarrassed to talk to their parents about this sort of thing but they shouldn't because it's not them who's done anything wrong.
"Also, from an early age, I've been explaining to my sons about what they should and shouldn't do on social media, pointing out where messages become inappropriate and explaining that girls can look a lot older than they are sometimes, which I think is important."
For more advice on keeping your child safe online, visit www.thinkuknow.co.uk/parents, www.everybodyplays.co.uk and www.nottinghamshire.police.uk/advice/prevention/online