She should have boiled the toddler’s mouth or done libun. 😉
Really, a baby is a baby, there is no aveira. The mom should learn from this and possibly refrain from having that type of chometz around for a couple of weeks BEFORE Pesach. I used to buy only Pesachdig nosh (just a little bit) for my kids the week before, so they did not bring additional chometz into the house. So if I found a cookie crumb, it was a non-gebrochts cookie (no matzoh or its derivatived prior to the Sedarim, after Purim), and I didn’t have to worry.
BTW, people who really are being sarcastic or mean to be funny (in their opinion), shouls use the 😉 symbol after what they write, to show it is meant in fun. That would go a long way to help prevent the situation when someone feels insulted where no insult was meant.