I have to agree w/you on this totally.
Caring for more difficult children is much more physically + mentally draining to a caregiver thus the caregiver should be compensated accordingly.
I think it is up to the parent to make this determination, not the nanny.
If I had a difficult child, I would naturally offer a higher salary to my nanny/sitter since I would understand she would be more stressed caring for my child over another.
Sadly, many parents are only out for themselves and are always trying to save a buck so this is not something that happens often.
Therefore the nanny/sitter must make this determination which she shouldn't have to.
