It's over twice the average weight of a 6 year old, so for all relative intents and purposes, it isn't wrong. I know fully grown women that weigh 92 pounds.
That aside, by no means does fuggs' kid look 92 pounds. The criticism isn't really directed at the kid.
Either fuggs is full of shit and the kid isn't actually 92 pounds OR if her kid actually is that heavy she desperately needs to do something about it as it would be a serious health risk.
As in, on one hand, fuggs probably shouldn't be lying about her kid's weight to garner sympathy ("I can't handle this kid who's too big to discipline") and on the other hand, if the kid really weighs so much, fuggs needs to take responsibility she's adamantly opposed to taking, and the resistance to taking responsibility in favor of gloating about the kid's appearance could potentially be extremely harmful to the child.
These are both criticisms of fuggs.