Hi Claire! I just wanted to welcome you to Yorkie Talk - congratulations on your Yorkie Baby and on your upcoming arrival!
We had a cat when I was pregnant with my son and one thing we were told over and over again was to make sure you never leave your child and any animal alone in a room together, even for a minute. I've followed this rule ever since and my children are now great with animals, but still not allowed to be alone with our dog.
Has Gracie ever been around babies before? If not, I would have a friend with a baby start to come over so that Gracie can get used to the sight and sounds that a baby will make. And as someone else said, just make sure that when the baby is napping that you give Gracie a lot of cuddle time - so she knows that she is just as special as ever!
Again, congratulations!!