Like they say, YORKIES are like chips, You can't have just ONE!!!
Go for it, you will see that your current baby will be much happier with a playmate. I got a female 1-10 and her brother 2-27, the difference in her was so amazing. As soon as we put him on the floor they started playing and have been inseperable since then. She is still a loving little Momma's girl and he is doing his best to take her place. Not that it will ever happen. LOL You will feel better about leaving your girl at home because she won't be alone. We feel better about it for sure. The even slept in the same crate the first night and all the time now.
Good Luck.......
Sharon, PIXI & SPIKE