Haha, to be honest Gabe, I'd be worried if she weren't stubborn with that mix! As for the going after animals that can hurt her bit, well, both breeds have tenacity in spades as well. She sounds like a Dachshund-Jack Russell-mix!
I think I might look into both of those: Wing Chun and Tai Chi. I think I'll also try and buy the book my brother-in-law has on Aikido -- he's who I learned a bit of it from, and he learned it while he was in the Marines. I had to give the book back, but would be nice to have my own copy. I like everything people say about yoga, about what it does for them, but it's just not my thing; I've never been interested in it, and it just seems too tranquil for me, I guess. I don't know, it's kind of weird. Using martial arts for the same thing is much more my speed in a number of ways.
The balance ball is a good suggestion (as is fiber, haha). I've always been hesitant about those things myself...maybe I'll give them a shot some day and incorporate them, too. Exercise balls are great, too. Apologies if you meant the same thing -- I think of two different things for each, so wanted to be sure both are brought up, I guess.