Don't worry to much, she is just adjusting to her new surroundings. I don't know any tricks to make her drink, but my guess is that she will drink when she is ready, and possibly already is when you aren't looking.
Also, if you are interested in what gender she really is, I would get the sexing done. It's not expensive and it's the only true way to know.
Blessings on the new baby,
Hannah