They said that she would be returning to Windsor for her convalescence. If they mean to her home rather than the Castle, then they don't have any live in staff their. They do their own cooking when at their Windsor home, and the Nanny does not live in either - not that she would personally help the Princess anyway.
As they probably need to stay in that area for the children's school, I imagine that she will be fine at their home in Windsor, as she is normally very fit. However, if they did still need some extra help for a while, I imagine that they would either decamp to the Castle, or, if it is within a reasonable driving distance to the children's school, to her parents home instead.
As for her reason for needing an operation, the only thing I will say is that whatever the problem is, it is not being resolved by using key-hole surgery, as that should not need such a long stay in hospital. Or maybe, as it is supposed to have five star hotel living standards, maybe she is staying in longer so that Louis can't just go running in and jump on her in the bed, or whilst sitting in a chair!
I hope she has a very quick and pain free recovery.