Caloric intake is a tricky one since I am not positive of how much she is burning but from what you have laid out there it sounds as thgough around 2000-2400kcal a day should be plenty, though maybe too much. Hell, it coul dbe slightly too little as well but I woudl start there. I think that will result in getting leaner and if she is eating enough protein and is working out properly should help take her physique to looking like what a triathlete's does.
I think triathletes tend to train a fair bit more than that usually though I could be mistaken, so most might ordinarily eat mroe. I would recommend and isocaloric diet for the most part (30/30/40 ois the ideal ratio of calories from prot/fat/carbs), though she may want to make it more like 50-60% of her calories coming from carbs.
As for types of food, I believe she will want high fiber, low glycemic-index foods in the am like rolled oats, brown rice, whole wheat pasta, yams, etc., simple carbs like gatordade and fruit closer to workout time. Hope that helkps - I am not a triathlete so these were suggestions. I woul ddo a little more asking around and then some to your own conclusions.