Hi Welcome to YT!
I say she is to young...you should wait until she is atleast 6 mos and a good 4 lbs or more...and keep in mind...she will be teething soon and sometimes not all the milk teeth fall out its very common with Yorkies and you will have to have her put under to have them removed...most people wait until around 8 to 9 mos before spaying to see if they have to have baby teeth pulled than you can have both done at the same time.
And I'm not sure but I do know my Vet will not put a 3 lb pup under...its very dangerous...I'm sure your breeder will understand and she should have told you about the spaying and milk teeth removed at the same time...it really is best and safer for your pup.
Don't forget to have a blood work done BEFORE letting the Vet put her under....Good luck
Here is a link for Anesthesia.
Anesthesia Protocol