Stacey McCance also branded Ms Hainey "a weirdo" and told how the curtains of her home, were Declan was found dead, were "always shut".
Tragic Declan's body was found in his rubbish-strewn cot in Paisley in March 2010.
Ms Hainey, 38, was convicted of murdering him and was jailed for life in 2012.
But last April she was released on appeal after medical evidence at her trial was ridiculed by a judge.
A fatal accident inquiry into his death heard yesterday from Ms McCance, who said her former friend avoided the house where Declan's body was found as often as she could.
Ms McCance, who lived opposite Ms Hain-ey in Bruce Road, Paisley, said: "She would always come and plank herself down in my house.
"She was never in her flat - she said she didn't feel safe in there. She never wanted to go near the place."
Speaking about the events of June 2009, Ms McCance said: "She said her ex-partner was giving her grief and she was scared of him. She said she had a room in her mum's and her mum's house was like a home from home."
She said Ms Hainey gave her the impression that she was spending a lot of time at her mum's house and was staying overnight with Declan.
The inquiry earlier heard from Ms Hainey's mum, Elizabeth Rodden, who said she did not see Declan after his first birthday in April that year.
Ms McCance also said that Ms Hainey's curtains were "always shut" and Ms Hainey said it was because she liked privacy.
The witness said she had once spotted Ms Hainey through her living room window, thinking she was looking down at Declan.
Ms McCance said: "She said, 'I don't like people looking in, I like my privacy.' After that, the curtains were shut and they were never opened again."
Ms McCance, whose own daughter was six when Ms Hainey was her neighbour, said Declan was "clean and quiet and well looked after."
She said she and Ms Hainey fell out just before Christmas 2009.
The inquiry, at Paisley Sheriff Court, continues.