Congrats! We got Yoda at about 4 weeks, and he was fine after a few days with us. Make SURE you get a harness and not a collar, as Yorkies are prone to tracheal collapse. Harnessses work a lot better for our little guys. My vet said you can fix them at around 8 months (at least for boys) I believe, so anytime after that should be fine. You should be able to bathe her now, just don't bathe her too often at first (once every week or two). You can brush her now too.