Sounds like a very odd "heat" period if it was one.
Right now I have 3 girls in season......one can surely bring the others in
.......and I certainly haven't smelled any type of odor as you are describing. They all wear bitch britches in the house which I have lined with diapers.....and for the first 1-1.5 weeks I end up changing the diapers daily because there is that much blood.....however after that it dramatically decreases. Again I've never smelled the type of smell that you are describing.
Also her coming in at 5 months sounds peculiar as well. My girls typically come in anywhere between 8-10 months of age. I believe my vet once told me that little dogs mature faster and they are typically in around the 5-6 month mark but larger breed dogs take longer to mature so typically come in later. I do know from hearing from people who feed raw that their girls come in even later and that it isn't unusual for a bitch to come in for the first time around a year or later.....
I've had bitches bred ~~ and have never had the pus as you have described either.
So it sounds unusual to me~~I think if she were my dog and I wasn't intending to show her I would probably spay her sooner rather than later as it almost sounds like a pyrometra type situation setting itself up for the future.
JMO
Heather Peters