AW11, when my DH and I need to lose weight, we do it together. In fact, you could have been my DH, a few weeks ago. My weight has crept up a bit recently, and so has his - although it isn't awful, we're bigger than is really healthy and I, at least, would like to look slimmer again.
My DH pointed out that we have a holiday in what was then 10 weeks, and that he wanted to lose weight, and how would I feel about going on a diet with him. Now he knew that I wanted to lose a bit of weight but needed to be kick-started, but he certainly didn't come out and say that! But it had the same effect :). In practice, we eat a similar breakfast and evening meal - I like weightwatchers online as I find it an easy way to portion control, but I tend to cook 2x 'my' quantity for the evening meal, as I can't be doing with trying to serve up uneven quantities of rice etc. But we have plenty of veggies etc. for bulking out that meal, and plenty of fruit for afterwards, if needed.
As a man, DH needs more calories than me. So, to support me, he eats those at work. He may have a beer of an evening, which bumps up his calories, but he generally eats in the canteen at the office at lunchtime. He can choose a salad if he likes, or chips if he likes. He tends to do his exercise in the evening, so on those days a lighter evening meal isn't a bad thing anyway. He doesn't feel short-changed, I don't feel that he's eating more in front of me while I'm on sparrow portions, and we're both losing about 2lb each week 
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Weightwatchers is easy and really helps with the portion control, so if it works for you, you might like to suggest it as something you do, and would she like to join you. The key is to find something that you can do together. DH likes the idea of the 5:2 diet, but I know that I can't do that whole sudden low blood sugar thing - it isn't good for me. So I suggested that he could do it, and I would support him, but I wouldn't do it myself. Instead, he chose to follow a diet we can do together. He's a keeper 
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