The people thought that a 4.5lb 4 month old pup was too big? It is their loss!
She may get a bit bigger but I have heard of some people being sold a "teacup" that was already 4lbs at 8 weeks! It is really sad that people want such tiny dogs. Such small sizes as the nonexistent "micro mini" are supposed to be can be a real handicap for the dog not to mention the health problems that crop up in pups that are bred by such people.
I hope you and your little guy do well together.