The offending happened in August 2014 after a 21-year-old Christchurch man contacted her online and the pair formed a bond.
The child's grandmother spoke of the incident outside court.
"How can a mother, supposed to be protecting her child from the paedophiles of the world, expose him to them," she said.
Police discovered the video when investigating the man, who is before the court on 16 charges.
Harvey told police she did it for the money and bought a laptop with the $300 given to her.
She was charged in June and admitted her role two months later.
Crown prosecutor Nick Dobbs urged Judge Recordon to take a starting point of up to seven years jail and said the final outcome had to be one of imprisonment.
But defence counsel Annabel Maxwell-Scott said her client had been systematically groomed and was highly vulnerable because of her own turbulent upbringing.
Harvey's son had been taken out of her care by Child Youth and Family and the court also heard her daughter was too.
Ms Maxwell-Scott said it was unlikely the defendant would ever see either child again.
Though she accepted Harvey's actions were "abhorrent" she said the baby appeared to be asleep while the video was being made.
Judge Recordon said the breach of trust was "at the highest level a mother could be involved with" but was not convinced jail was the answer.
"You're someone who very clearly has never been able to form an attachment with anyone. Your life has really been a mess until now," he told Harvey.
"Prison would be a Band-Aid covering over your issues."
He said she needed psychological rehabilitation, which was best undertaken within the community.
"You're a fairly simple soul capable of leading a productive life. If you go to prison I think it would put the kibosh on that," the judge said.
Outside court, the victim's grandparents said they were not convinced Harvey had any remorse for her crimes.
"She didn't need the money because there was food in the fridge that we provided."
Now all they were concerned about was raising the child.
"It might not have an impact on him now but in the future it will," they said.
"We're the ones that are going to have to explain what happened."
Judge Recordon also sentenced Harvey to a year's post-detention conditions and 100 hours of community work.