Daynes lured 14-year-old Breck to his flat and launched a 'sexually or sadistically motivated' knife attack in February 2014.
But in the online posts Daynes claims Breck attacked him first – because the younger boy had anger problems caused by his family.
Miss LaFave told the Daily Mail that the killer, who was jailed for life last year, was lying to torment her.
'Everything that he does is with the intention of controlling and manipulating people,' said the 48-year-old.
'He is a convicted murderer who is able to use the weapon of the internet to harass my family. He is taunting me from behind bars and the system is allowing him to do it.'
It was unclear last night how Daynes posted the blogs, which can be seen on his Twitter account.
The Prison Service insists that his cell was searched after the posts appeared and that no electronic devices were found.
A spokesman added: 'Prisoners are banned from using mobile phones and social media. If they break the rules they will be disciplined and can have time added on to their sentence.'
The first note was posted on November 26. Miss LaFave, who was born in the United States, believes it was timed to clash with Thanksgiving celebrations that day.
It claims to offer comfort to Breck's family by saying 'his death ensued seconds after the injury' in a fight.
But the blog then alleges the teenager was subjected to 'drunken, abusive behaviour' at home which drove him 'away from family life and towards the virtual world'.
