Have a look at google books. There is a book called 'Register of appointments to the household of Queen Mary II' (or similar - I've accidentally closed the page!) published 1689, but not apparently digitised. It looks like this might have the information you are after, assuming your possible ancestress was in Royal service from the start of the reign. Whether you could access a copy of this book anywhere is another matter. Otherwise the Royal Archives at Windsor would probably have this sort of information.
