Dungannon Crown Court heard that 27-year-old Martin put the changes down to Millie possibly being "a wee bit jealous" of her then lover Barry "Budgie" McCarney.
Martin, who made the claims to police while initially being questioned as a witness, not a suspect, also told of unexplained injuries to Millie, including bumps to her head and a claim from McCarney she had taken a tumble out of her cot.
Martin, from Main Street, Kesh, is accused of wilfully neglecting and allowing Millie's death, while 33-year-old McCarney, from Woodview Crescent, Trillick, denies not only her murder, but sexually and physically abusing the child.
Reading from one of her video-taped interviews, designed and known as "achieving best evidence", a detective said Martin claimed that in the past Millie had been "playful .... affectionate".
However, she then became "clingy at home" always standing by her as she worked, pulling at her trouser leg. She also noticed that in the mornings, instead of playing with her toy mouse Mimsy, "she just lay in her wee cot", although she put this down to Millie just "being good", or "having a wee lie in".
The jury of nine men and three women heard that the child was fine in her grandmother's, and while she "never made strange", she was different at home.
"At home she didn't really go near Barry that much," however, Martin told police again she "thought it's cause she's jealous of him being with me ... she may have felt a wee bit jealous".
Martin also told police of an unexplained "lump" on the child's forehead. She said McCarney had called her, telling Millie was "blue around the mouth".
However, when she rushed to the bedroom, what she noticed more was the injury to the child's head, which McCarney claimed, "oh sh-t, or oh f--k I never seen that".
Martin told police you could not have missed the injury, but what surprised her more was the fact the child wasn't crying.
"I can't, I can't understand how she didn't cry, how she wouldn't cry," said Martin, who added later if she had somehow bumped her head she would have "squealed" and complained about it for days.
The court heard of another occasion when she went shopping to Asda having left Millie in her cot sleeping, when she got a mobile call from McCarney saying he'd heard a "thump" and that the child had fallen out of her cot.
Martin told police she couldn't understand "how did she do that", and while it may have sounded "silly", Martin said she "just thought maybe she was sleeping walking".
The trial has now been adjourned for the mid-term break, to continue on Monday week.