Don't be on "whatever diet" -- for some people, you can train until the cows come home, but if your diet isnt' there supporting what you are doing, you are pretty much wasting your time.
What is her height, weight & bf right now? Its not like she needs to go on a wild all-restrictive diet, but if you expect to get any kind of results in a safe & healthy way that can be adapted into your lifestyle, you really need to clean it up & make some tweaks. Diets that come in packages w/ names on them (e.g. Atkins) are not complete diets that are lifelong additions to your lifestyle. They are designed for easy packaging & marketing or to provide some "quick" result that most people can't maintain anyway.
I"m not suggestign to go find a "named diet" - but rather building a program that is easy & adaptable and works for her current body demands. The short answer is to have her get a copy of Bill Philips' BODY FOR LIFE book - the reason I mention this after dissing "named diets" is that it has a great intro to nutrition (i.e. WHY you eat a certain way) and also the program provides lots of guidelines which allow lots of flexibility in what you eat as opposed to diets that tell you to suck on grapefruits for 30 days or some shit.
What I'm saying is that there's a little more to getting good results than just "do this list of exercises every day for 3 weeks & you'll be ripped up & lean". BODY FOR LIFE does a good job of explaining it & providing an excellent basic program w/ lots of flexibility. I dont know how interested your lady is in spendign time "learning" stuff - maybe just expects to get a list of exercises & voila! Takes a little more than that, not much more, but a little more. And of the 3 (diet, training, cardio) diet is by far the most important.