Crown Solicitor Amanda Gordon told Justice Tracey Walker this morning Thompson handed herself in about 8.15pm on Thursday.
"She told police she wanted a couple days of freedom and now wanted to come and own up."
Thompson faces four charges, including murder, injuring the child with intent to injure and two charges of ill-treating a child.
The 18-month-old died in Waikato Hospital on July 24, 2018.
The trial was delayed each day until Thursday when Justice Walker dismissed the jury panel, advising them of the situation.
Justice Walker remanded Thompson in custody to reappear in the High Court on February 19 at 9am for a callover.