First off, congratulations on your new addition.
Just so you know, there is no such thing as a "miniature yorkie". All yorkies are considered members of the toy group, no matter what their size- though AKC standard does say no more than 7 pounds to meet the standard. Mini/teacup/pocket pup are terms used as marketing ploys. And it's almost impossible for a breeder to promise you she's going to be a certain size- there are just too many variables.
I have a nearly 10 lb male and a 5 pound female. You will have to be careful in the beginning to make sure your boy doesn't play too roughly. Or in my case, that the girl doesn't egg the boy on to play too roughly
She's my fierce diva and he's more of a laid back dude. Even though he's gentle with her, sometimes they do get carried away. She has no concept of him being bigger than her and she tries to keep up with him at every turn. When they aren't fighting over the same toy, they are the best of friends.
Just make sure that when you bring her home, Coco know's he's still number one dog. Feed him first, talk to him/pet him first. There may be some jealousy issues at first, but if he likes being around other dogs, then I'm sure he will do fine with her.
Good luck.