i think your boss just wants you to rest.
anyway no one will replace a perm with a temp staff becoz they need to train from beginning again which is inefficient also.
normally they are there to help out some general office tasks only. And perhaps she thinks that she can afford to pay a temp staff so that you can rest more also?
and anyway you are kind enough to offer work from home options...in which she should be grateful for that and wonx get rid of you.
from what i see its a fine arrangement.