Does your little girl have experience with other dogs and did she seem to like being with other dogs?
Everything depends on individual personalities. My first boy, I always called an only child and in many ways I think he would have been fine being the only one. However, I added a second, and they are best buddies. There was an adjustment period, but they truly enjoy having each other. They are not self-entertainers, meaning they both still want their humans to play with them, but they are improving. They will chase and play tug-o-war more now on their own.
If a second dog fits your lifestyle, I say go for it.
