If you do go with the 6D keep in mind that the practical focal length of your lenses will shift with the full frame.
If your wife likes the look of a 50mm lens, then with the 6D, that's going to require an 85mm lens to replicate the look. Fortunately, if you don't already own it, the 85mm f1.8 is a good quality, inexpensive lens.
If you are used to using a 70-200 on the t2i, keep in mind that you'll need a 300mm lens to replicate the look on full frame.
On the plus side, the 70-200 mm can substitute for the 50mm from a focal-length perspective (although it will be a slower lens).
Personally, I'd go with the 6D if you live in the U.S. Canon Price Watch has just posted a $1,899 deal with a 24-105 zoom. Unfortunately, Canon's refurbished store just ended their sale, where you could get a 6D body for $1,300.