Well, I do believe that is normal Yorkie behavior, she may be letting you know that she is over stimulated and needs a rest. I know that there are 2 kinds of yorkies the "cuddlers and lovers" and the "independent" kind.
Our Millie is the "independent" kind. She does need alone time and if she gets "over stimulated" we will put her in her play pen area and she gets quiet and settles down.
If we pick her up and she does not like it she will growl, if we do something she does not like, she will growl. (she has a bit of a temper). Now having said that, we let her know we will not tolerate that behavior. We have to show her there are other acceptable ways to let us know what she wants, or she needs to tolerate what we are doing, because it needs to be done.
Unfortunately, when you have one of these types of Yorkies, it does require a bit more work because I am constantly showing her who is boss. But after about 2 months of this "fight", I am winning and she is coming around.
I know I will have more fights in the future, but she really is becoming a real sweety, is much more "tolerant" now, and loves to be around me
but she is not much of a cuddler yet, but we are working on that too, and she is showing some improvement on that part too.
she is only 4 months old yet, so I have plenty of time to work with her.
I am lucky, because I have such a strong personality and want to be in control and boss, Millie really has no chance
I will win this battle! But we are having great fun!