[Amazing Yorkies]

Yorkies have small tracheas and we highly suggest using a halter instead of collars to avoid collapsing a trachea. Personally as active as they are, I worry about getting hung up with collars and choking.
In answer to your question, she is very young so I wouldn't worry about using anything until she is closer to 12 weeks, normally when our babies go to new homes. Watching for low blood sugar is important at her age.