From my experience, hounds that track another dog at a young age do it because they are putting two and two together. Dog track equals rabbit track as well. In other words, the young hound is usually pressured too much at a young age, and learning that the other dog is going to produce what he/she likes best, and that is the rabbit. Makes sense to me why a young hound tracks another dog, because when they are behind in the chase, usually do to lack of experience, they are smelling both tracks, the other dog(s) and the rabbit. My suggestion would be to run this young hound solo or with another dog that she can run the front on. Usually, hounds come out of tracking other dogs with age, and confidence because they begin to rely on themselves instead of another hound. But, on occasion, I have seen dogs that will track another dog at six months, and at six years! Good luck with your young hound. I put too much pressure on my young hounds as well do to time.

After reading my own post I am going to solo a few young hounds myself, and practice what I preach.

Hope this helps a little.
I am editing this post because I forgot to answer the second parts of your questions. I have seen young dogs that naturally can circle their own rabbit at a young age, but I have also witnessed the opposite. (Some never will be able to do it alone.) Some will come on with time. Patience is always key. On the other hand, and I still believe this myself, what a dog does on its own is really what the dog truly is. The dog can't hide anything when asked to perform by himself/herself. Good luck.