If she was about 1 pound 9 oz (25 oz) at 8 or 9 weeks then she probably will stay in the 4 to 5 pound range, but if she was only 6 or 7 weeks she will probably be bigger than that.
Most guarantees state a specific time limit (usually 24 to 72 hours) for notifying the breeder of any problems discovered at the vet appointment. An initial vet consultation isn't that expensive and I would definitely recommend it. He'll be able to listen to her heart and lungs, check her knee joints, etc. Bring in a fresh fecal (#2) sample so he can check for parasites (worms, giardia, coccidia, etc.)
Make sure you have Nutrical, Nutristat or Nutridrops on hand. The nutridrops are faster acting and longer lasting, but are sometimes harder to find. Give it to her the minute you can and bring food and water with you. You might want to buy a jar of baby food pureed meat to get food into her as quickly as possible. Also ask the breeder to give her Nutrical right before putting her on the flight to you. I would continue to give it to her 3 or 4 times a day until she settles in. You will also need to feed her at least 4 times a day. All of this is to try to prevent hypoglycemia (low blood sugar). You can read about hypoglycemia at
www.glassyorkies.homestead.com just select hypoglycemia on the left.