I have been reading all of your wonderful advice for a couple weeks now, anticipating the arrival of my first yorkie

He will be 12 weeks on the 13th and I have been making plans with the breeder to pick him up on the 10th.
She just wrote me wondering if I could wait till the end of February to pick him up because he is not eating very well on his own. Does this sound right? at what age do they start to ween them from thier mothers? I feel she is only doing what is right for the puppy, it is just soooo hard to wait and all the plans we have made to pick him up. I even have a week off vacation and we are driving 600 miles.
Please help, I don't know what to do, is this something that seems normal. He weighed 1.6 at his vet check at 9 weeks and she said he was healthy.