I buy a lot of produce at the 99 cent only store at 35th Ave and Peoria. They have 5lb bags of potatoes, 3 heads of romaine lettuce, bags of spinach, bell peppers and bags of fruit for $1! You do have to use it within a few days but I shop 2-3 times a week for produce anyway (4 kids... nothing lasts long in the fridge around here).
Also, she can try the FoodValue club at the West Side Food Bank. For $30 you get a box of pantry staples (rice, pasta, soup, peanut butter etc.), a box of meat (chicken bresasts, ribs, hamburger) and two "bonus boxes". The bonus boxes can have anything from breads and cookies to produce or flats of Gatorade. My kids love the bonus boxes because it is usually full of stuff I would consider "treats" and wouldn't regularly buy. You don't have to "qualify" or anything and it is not charity...it just allows the food bank to make money on items that may be expiring soon. You get a deal, they get money to help those truly in need.