I had a mare like that. She would go absolutely anywhere except back home. I normally don't believe in giving treats when we get back to the barn, but I did with her. With my horse, I think it was because she was confined to a small paddock and was bored. When I moved her to a new location, she did much better. She ended up being one of the best trail horses that I ever rode. I believe that it you asked her, would have taken you through the pits of Hades just to see what was on the other side.
Feed her a bit of something sweet when you get back home. Also, go on longer rides. She will most likely get better.