Where did she raise the chicks and what flooring do you use in the brooder area?
I haven't had any of our broody chicks get pasty butt, however there are numerous possible causes so rather than just assuming it was bad mothering I would consider other environmental factors also.
Not all hens are wonderful mothers, some are stellar no matter what the situation is, many do well with minimal assistance (such as privacy help the first week or help rounding up the littles in the evening the first few outside trips)and some need privacy throughout to keep them on track and frequent interventions to keep everyone safe.
Thankfully the full assistance broody is rare, as are the really poor broodies or the ones who never bond with the chicks when they hatch and attack the newborns because they don't transition from sitting mode to mama mode. Sometimes poor human planning causes poor brooding and the hens get blamed and sometimes the poor or borderline hens can improve with a bit of help and experience. Some are just too scatter brained to ever really settle in to good brooding.
There are just a ton of factors at play so often it means weeding through possibles to find the probables....and there are no perfect answers...
Pasty butt with a broody would be caused by the same factors as pasty butt in an incubator chick raised in a brooder...
