Welcome to YT
A female needs to be at least 5 or more lbs to breed. But that alone does not mean that she should be used to breed. Where did you purchase her from? Did your breeder give you breeding rights? Do you know about her background and others in her background? Where are you planning on getting a male to breed with and do you know the background of the male as well?
These are all questions that you NEED to know the answers to well in advance to even considering to make puppies with your little girl.
Then there is the fact that if you decided to not breed her as well as not have her spayed, there will always be the chance that puppies will be made on accident. When a female goes into heat there are male dogs from very far away that will be able to smell that she is in heat. What if she is in the yard and a much larger dog were to try to mate with her. The complications involved with that could be life threatening.
