Like what was said, local show halter winnings don't mean much. It can help to say how many were in the class. Who knows--your horse may have gotten second out of 2 of 2nd out of 200....it makes a big difference.
Have you had other knowledgeable horse people evaluate her conformation? Not saying that you are, but there are a lot of barn blind people out there that think their horse is the greatest thing since sliced bread, but really its just an average mini.
I am not trying to be mean, but I want you to understand the reality of the situation. From the description given I would price the horse at $500- $1,000 and be prepared for lots of low ball responses. Showing it also a good way to advertise. The more people see your horse in action and how great she is they will be more interested in purchasing, just choose your shows strategically.