In upholding the 20-month jail term handed the Toronto resident, who can't be identified, Ontario's top court said it saw no reason to interfere.
Court records show the mother of three, described as having "strong religious convictions," had returned home from work as a nurse to be told by her son that his 10-year-old brother had disobeyed her by taking food from the fridge and eating it.
The boy denied doing so. His mom ordered the older child to get the iron and plug it in.
"She then embarked on a lengthy interrogation of the victim in an effort to obtain a confession from him," according to the Ontario Court of Appeal decision. "No admission was forthcoming."
She then used the iron to scald her hapless child on one arm. When he still refused to confess, she burned the other arm.
Despite being a nurse, she neither provided nor sought any medical assistance for his second-degree burns. A gym teacher at school noticed the wounds and called police.
At trial, a jury convicted her of aggravated assault and assault with a weapon. The judge jailed her for 20 months in July 2013.
The mother had wanted the Appeal Court to cut the sentence to five months.
Among other things, court heard the woman, who showed no remorse for her actions, had no prior convictions and was gainfully employed.
A psychiatric report described her as suffering from a personality disorder involving "substantial moral indifference and a striking lack of capacity for self-doubt."
In throwing out her sentence challenge, the Appeal Court rejected her characterization of what she had done as nothing more than "excessive discipline."
"This offence involved an egregious breach of trust, consisting not only of the abuse of a child of 10 years, but also of the recruitment of his older brother to bring the tools of that abuse to his mother, the abuser," the Appeal Court said.
The panel also rejected the argument that the woman, who had immigrated in 2006 from Nigeria, should be given less jail time because the higher sentence means she will likely be expelled from Canada.
Imposing a lesser punishment to avoid immigration consequences would simply not be appropriate given what she had done, the court ruled.