That's a large weight increase. Has she had her hormone levels tested to see if there is an imbalance that needs to be addressed?
As for diet, I recommend eating 5-6 small to moderate meals per day, every 3-4 hours. Choose whole foods over processed foods. Earlier in the day, the meals should be composed of lean protein and complex carbs. Later in the day, meals should be composed of lean protein, healthy fats, and fibrous carbs.
Protein sources: lean beef, chicken, turkey, fish, eggs/egg whites, protein powder.
Carb sources: whole grains, vegetables, fruit
Fat sources: nuts, nut butters, olive oil, macadamia nut oil
Essentially, take out as much refined and processed foods as possible and replace with whole foods.
Any broad spectrum multi-vitamin should be ok. I personally take Now brand Eco-Green Multi.