Welcome to YT, Hair type is in the genetics of the dogs the parents, grandparents, great grandparents, etc.
Your title is "Biewer Yorkie".
There is no such thing as a Biewer Yorkie, you either have a Biewer or you have a Yorkie. These are 2 different breeds, the only thing the same between a Biewer and a Yorkie is the are both in the terrier family.
Shaving her down may not get you the coat you are looking for.
Here is a link (one of many) on the Biewer Terrier.
Biewer Yorkshire Terrier | Informational Center