J.N.
Instead of a sippy cup, start teaching her to drink from a regular cup. She is definitely old enough, and that will spare you the trouble of weaning from the sippy in a couple of years. Yes, it is messier to start with, but anything other than a bottle should be given at the table (or high chair) anyway. You can start with the milk she is used to (I assume you are pumping?) or white grape juice or even water. I started teaching my kids to drink from a cup around 6 months old, and they were pro's at it within a month or so. (You/the nanny will have to help her hold it for a while still)