*This thread is worthless without pics!*
that said, i'm 6'2" and a little over 100lbs heavier than your wife (i'm a dude though) if i lost 50 lbs, i'd think i was in shape, if she weighs another 55lbs less than that, at an inch shorter it is my assumption that she has a smokin' hawt body.
i think a lot of it is genetic. i have a huge butt that stays huge even when i used to be thin. no ammount of excercise short of cocain addiction or bulemia is going to make that go away. sounds like you wife already looks fine, womenses are supposed to have curves.
good luck, and we are patiently awaiting pics. lol.
(i hope i haven't offended you, i was just trying to be funny)