not knowing anything else than what you have written....ramp up the cardio. daily sessions above and beyond the wod. if the wod is a butt kicker, like the filthy 50, then, naturally cardio is not necessary. but on days with the M.E. lifts or wods lasting less then 20 minutes i would have her add some moderate (i'm sweating and a bit uncomfortable) cardio for 30 mins or so.
as for diet, i assume you mean you are eating the same things but she is eating less of it. your calorie requirements are going to be higher than hers so her portions should be 1/4 to 1/3 smaller than yours. calorie in...calorie out.