It doesn't really matter if she's a vego or if she eats small children. She needs to decrease her calorie intake, increase her energy expenditure (preferably with high quality weight training), and work out a mcaronutrient balance which she eats 5-6 times per day. 50:30:20 or 40:30:30 ratios are a good place to start with 12 times her bodyweight (in lbs) for calories.