Healthy Weight Gaining Foods/Recipes?

So here's the story. My gf, who is in the hospital for CAD, is being released. She is doing a lot better now. She told me that she's gonna gain weight fast by eating fatty foods, such as fast food, which got her in the hospital in the first place. I need your guys' help. My questions is : Do you know any healthy diets that will let her gain weight, but also be healthy for her and her heart? Please, any help would be appreciated. And if you know any good healthy recipes/foods please include them! Thank you!