Does Tina's fighting stance exist?
Well, to the best of my knowledge, maybe.
Back when I took Tai Chi (before I learned it was tougher than Yoga), I learned a stance in the Simplified Yang 24 that looks a lot like what Tina is doing. I believe it's called "Golden Rooster Stands on One Foot."
Generally, though, they make it up in kung fu movies, too, so I wouldn't worry about it too much.
- Akhmed Al-Fayyed