Oriwa Kemp admitted assaulting Nia by throwing shoes at the toddler.
She also pleaded guilty to charges of assaulting two other children, also by throwing shoes. The incidents happened between the May 21 and July 20 2007.
Wiremu Curtis pleaded guilty to assaulting two children - not Nia - by performing wrestling moves on them.
The other children cannot be identified for legal reasons.
Oriwa Kemp is also charged with manslaughter and cruelty to a child over Nia's death. Wiremu Curtis - who is the partner of Nia's mother - is also charged with murder and cruelty to a child.
Nia Glassie's mother Lisa Kuka, 34, is charged with two counts of manslaughter - one for failing to provide medical treatment and another for failing to protect the toddler - and Wiremu Curtis' brother Michael William Curtis, 21, is charged with murder, assault and cruelty to a child.
Michael Paul Pearson, 19, is charged with manslaughter, acts of cruelty and assaulting a child.
This morning in court, the registrar read out a long list of charges against the accused that included putting Nia in a clothes dryer and turning it on as well as spinning her on a clothes line.
Much of this morning's session was taken up with selecting the jury. Each of the lawyers representing the accused were given six objections while crown prosecutors were given 12 in total.
Justice Judith Potter excused many of the jurors after warning them that they should speak-up if they felt they were not able to be objective or impartial.
The high profile case is expected to take four weeks wit the Crown expected to start its case on Tuesday morning.
- Additional reporting DAILY POST
