But Kuka turned a blind eye, she confessed in an interview on October 9 2007 with Detective Sergeant Garry Hawkins.
"I thought Wiremu (Curtis, her much younger partner) would never hurt my girls -- and yes, I was in love with him," the 35-year-old said in a fifth video-recorded interview which was played in Rotorua High Court this morning.
"I wouldn't say that I didn't care what was happening to my daughter but yeah my loyalties were with Wiremu."
Mr Hawkins: "Did you ever think about taking Nia and leaving, taking her out of that environment to safety?"
Kuka: "To be honest, yes, but I also would have taken Wiremu."
When Mr Hawkins reminded her that Wiremu had been doing wrestling moves on her children, she agreed her loyalties to Wiremu Curtis clouded her judgment.
Kuka said there was one time she saw the wrestling move "pedigree" being done on Nia on a mattress in the lounge.
"Because I wanted to go somewhere, I just walked out the door."
She said she had "never ever" heard anything about her nephew, Michael Pearson, being involved in the abuse.
"To me he is my heart. He used to look after my kids."
Oriwa Kemp, Michael Curtis' partner, would "whack, whack, whack" Nia.
"I am not saying I never ever smacked her but I never smacked her like that -- with an open hand across the face, across the head, across the back. Why? Because she was ugly."
Kuka told Mr Hawkins that Kemp often said Nia was ugly.
When the other adults in the house whacked Nia the toddler would fall over and cry. They would tell her to shut up.
"What would I do? Nothing, just sit there."
Kuka is on trial for Nia's manslaughter -- for failing to provide medical treatment and failing to protect her daughter from violence.
Wiremu Curtis, 19, and his brother Michael Curtis, 21, are accused of murdering the little girl. Also charged with manslaughter are Pearson, 20, and Kemp, 18.
