Have you had her long, or is she a recent adoptee?
If you've raised her, then welcome to the
My-Yorkie-Won't-Come-When-Called Club. I just posted somewhere else that I think it's in the (secret?) Yorkie Union handbook that they "must remain aloof when called by the humans"
It is important to have her attention, in case she's in danger and you need to get her to you quickly. Try treats, or a favorite toy to make "coming" a positive experience. Lots of kisses and praise when she responds correctly. Obviously, you can't feed her just for obeying the rest of her life, so gradually cut out the treats, and just praise her. Doesn't have to be a big fan-fare event, just "good girl for coming" in a soothing, matter-of-fact tone.
And then - they STILL don't always come! LOL Good luck.