"For anyone, let alone someone who is also a parent, to take a picture like that and stick it on Facebook for a laugh is unbelievable. It's no wonder people are angry about it.
"People in the town have been talking about it, because anyone who has seen it has been left shocked."
Ms Stewart claimed that the boy, who is small for his age, climbed into the machine of his own accord, and criticised those who reported her to police, calling it "absolutely ridiculous".
She said: "He is clearly laughing in the pictures. So I don't understand why somebody took that picture as - well, I don't know what they took it as.
"What did they think I was doing to him? Taking him for a spin?
"He's got a bit of a washing obsession. Anyone who knows him would know he's got a washing obsession.
"I don't know who reported it. I don't really know why they would do that. I think it's absolutely ridiculous."
Ms Stewart took down the photo from Facebook after she was reported to the police.
"It's horrible having the police at the door thinking you're a bad person," she said.
"I was shocked, but in a sense I'm glad they didn't just take it as a joke and not come and see me. So I was thankful in that way."
She added that two police officers questioned her for over an hour before leaving without pressing charges.
A police spokeswoman confirmed Stewart had been spoken to. She said: "Advice was given. Relevant child care checks were made."
Ms Stewart said that since posting the picture last Thursday, she has been physically attacked by a complete stranger.
She said: "I got assaulted by a woman. She came to my door and said I was a f****** nutter and she wouldn't let me anywhere near her kids.
"It happened on my doorstep at 11 o'clock in the morning. I got assaulted in my own home."
A 42-year-old woman was arrested over the alleged assault. She appeared at Paisley Sheriff Court on Monday and the case was continued without plea for a week.
A spokesman from Renfrewshire Council said: "We can't comment on individuals but we are vigilant on any issue which could potentially affect the welfare of a child."