The father, Russell Simpson, who knew Dolly and her family, has posted the anonymous message that 15-year-old Katelyn received via social media app Snapchat.
Posting an image of one of the messages to Facebook, Simpson writes: 'Righto Lets see if everyone is fair dink-um about this social media bullying.
'To all the people that think we go on and on about Cyber bulling here is your example to what Katelyn has put up with over the years. It doesn't worry her anymore but now it has become to the point where OK here I come and look out.'
Mr Simpson claims he is on a mission to track down the anonymous user, and has 'narrowed it down to 5 [people].'
The horrifying incident comes just days after the nation was shocked by the suicide of Dolly Everett.
Dolly’s father Tick Everett encouraged parents to check in with their children and for young people to 'be kind and do it for Dolly'.
The family has established a foundation, Dolly’s Dream, to prevent bullying and youth suicide, with Mr Everett saying he would 'fly to every school if I could'.
If you or anyone you know is seeking support, call Lifeline on 13 11 14 or visit lifeline.org.au.
Kids Helpline 1800 55 1800 (for young people aged 5 to 25).