My sidekick rode a small Gary Fischer Super Caliber for years. She's now riding a medium Specialized Camber, which measured out close to the small SuperCal. She tried a small Stump Jumper FS but didn't like it. All 29ers.
Best thing is to demo as many bikes as possible in small and medium until you find the one that's right. I know, easier said than done. Some NEMBA events provide a good opportunity to try different bikes back to back.
The Turner Burner 650B looks mighty fine, looking forward to trying it out.