I know someone who years later is still traumatized making Pesach…the mother can’t forgive herself, despite feeling that she had cleaned meticulously at that time.
None. The child is obviously not responsible. If the parents thought they did a good job of cleaning but somehow missed this one piece by accident, then, at worst, it’s a shogeg.
If you find chometz on Pesach*, you have to burn it**. Period, end of story. No other halachic consequences.
She said that she was told she gets kares, that the parents r responsible for the child eating chometz.
Whoever told her that was a fool. You get kares for *intentionally* eating chometz on Pesach. Did the person think that she deliberately handed her kid a pretzel?
And, even if, for whatever reason, you want to say that she does get kares, it sounds to me like she’s already done teshuva — she confessed her sin, she has regret for it happening and she’s resolved not to let it happen again.
The Wolf
* Assuming, of course, that it’s an accident and that you didn’t intentionally keep chometz over Pesach.
** Keep in mind that if you find it on Yom Tov or Shabbos, it is muktza and must be covered over until after YT/Shabbos and then burnt.