If she's sedentary and unlikely to change that aspect, then her protein need will be a lot lower, probably only about 1g/kg/day. If you mean her job is sedentary, but she does (or will) do some regular exercise before/after work, then bump that up to 1.5-2g/kg/day. Other than that, normal rules: 1g/kg/day in fat consumption, and whatever's left over can come from whatever - protein, fat or carbs.
You're probably better off overestimating her starting calories than underestimating. If she starts out eating too much to lose weight at a decent rate, you can just step her calories back by 200 until the weight starts coming off.
Obviously, without knowing your wife's medical history/injuries/interests/etc, I'm gonna be inclined to recommend that she include training in her plan. I expect that I don't have to tell you why.