That's great that your vet has assured you that she's worked on many small dogs.
Some do wait til their little one has reached 3#'s to get spayed & neutered, maybe you can safely wait another month so she can grow a little more & gain a little more weight? Getting spayed & having any retained baby teeth pulled @ the same time is ideal so the little one doesn't have to go under again. Both Princess & Turbo got fixed when they were 6 months old & both did very well, I think they were around 4-4.5#'s. Their sister waited til she reached 3#'s & got spayed much later @ around a year old, but luckily, she never had her 1st heat yet. Best of luck to you & Hollee!