I don't know if one so young can get pyometra, but being that it is an infected uterus I don't see why not. It's usually associated with middle age dogs that have been left intact, I've not heard of one so young having it, but to be safe I would call my vet.
Pearl's only discharge were a few drops of blood, there was no pus like is mentioned in some of the articles I read.
More info:
http://www.petside.com/health/petvet...tra-canine.php
Since I've become friends with our vet and she takes care of my rescues, she will often let me assist her during s/n surgery. I was able to be there with Pearl and the vet showed me the infected uterus, there was no question....it was pyometra.
I know your girl is small, is that the reason you've held off getting her spayed? My Ruby was right at 3lbs at 13 months, and I did have her spayed with no problems. I would recommend having pre-op blood work done, as well as monitoring during surgery. I didn't realize that monitoring during a s/n isn't routinely done by all vets.