Possum Food

1. For Short-tailed Opossums
2. 
   Step 1
   Feed your pet opossum a high-protein, low-fat dry food. You can use cat, kitten, hedgehog or ferret food for your opossum. A dry food with at least 30 percent protein, 9 to 15 percent fat and 5 percent fiber is ideal.
3. 
   Step 2
   Leave the food out at all times. Opossums won’t overeat, and keeping your pet’s bowl full will make sure she doesn’t get hungry.
4. 
   Step 3
   Supplement your opossum’s dry food with a few insects or small pieces of cooked meat daily. If using live insects, purchase live mealworms, waxworms or crickets from a pet store to ensure that they are disease-free. You can feed your pet freeze-dried or frozen insects if you prefer.
5. 
   Step 4
   Add a variety of fruits and vegetables to your pet opossum’s diet. Use fresh, frozen or pureed fruits and vegetables. Experiment with a wide range of fruits and vegetables to see what your opossum likes best. You might start with apples, melons, berries, corn and cucumbers. Remove uneaten produce daily.
6. 
   Step 5
   Supply your opossum with fresh water at all times. Short-tailed opossums are prone to dehydration, so even a short time without water can have severe effects.
7. 
   Step 6
   Supplement your opossum’s diet with small amounts of cooked, boneless poultry or fish, or insects such as crickets and mealworms. These are good sources of low-fat protein.
8. For Virginia, or North American Opossums
9. 
   Step 1
   Feed your Virginia opossum a varied and omnivorous diet. Because Virginia opossums don’t do well on commercial pet food, a zoo-quality omnivore food is recommended. You can find this food through Mazuri, a company specializing in products for exotic animals (see Resources section).
10. 
    Step 2
    Provide your pet with a variety of fresh or thawed frozen vegetables. Your opossum might like almost any type of vegetable, so try out an assortment to see what he likes best.
11. 
    Step 3
    Include small amounts of dairy foods for calcium, whole grain foods for fiber, almonds for essential fats and a few drops of apple cider vinegar daily to help your pet’s digestion.
12. 
    Step 4
    Treat your opossum with fruits a couple of times each week. Try out a variety of fruits to see which she prefers to eat.
    
13. 
    Step 5
    Add garlic juice to your opossum’s diet to help keep her flea and parasite-free, and add virgin olive oil to keep her fur healthy.
14. 
    Step 6
    Provide fresh water at all times.

I Googled "care and feeding of a baby opossum" and came up with many helpful links.  If your friend does not have a computer, maybe you could do it for her.

  Services Prices FAQ Links About me Contact I KNOW FOR FIRST HAND THAT THEY CAN GET BIG HERE IN FLORIDA.  YOU MIGHT THINK THEY ARE DEAD  BUT THEY AREN'T. THEY WILL BITE ( BIG ONES ) IF BACKED IN A CORNER,
HOPE THIS HELPS
GOD BLESS
NANADEE
Orphaned Opossums & Injured Opossums
Opossum orphans need emergency first aid and then very specific care. ... information found on the Web. An important note regarding formulae: We are also ...
www.opossum.org/orphans.htm - 17k - Similar pages
=========================================== ALSO  I FOUND THIS FOR YOU
Opossum Info: Opossums are the only North American marsupials. The females of this group have a pouch on the belly where the young are carried and nourished for a time after their birth. Opossums are 2-3 feet long including the naked scaley tail, and weigh 8-14 pounds as adults. They live in a variety of habitats. The are nocturnal animals. Opossums are omnivores, and will eat almost anything, including insects, snails, rodents, berries, fruit, grasses, leaves, carrion, pet food, and garbage. They prefer meat to vegetables.
Biology: Opossums have many unusual physical features. As stated, they are marsupials. The females have 13 nipples upon which the young cling, as they grow in the pouch. As they get older, they push each other off until about four are left, then they leave on their own. They are famous for their prehensile tail, which they use for balance and grasping, and can occasionally hang from, though this is rare. They are also known for "playing possum", a defense tactic of mimicking death when frightened. They have opposable thumbs, and are excellent climbers. They usually only live 2-3 years, even as adults. The males have a bifurcated penis, which led to a myth about them copulating through the nose. They have 50 teeth, which is the most of any mammal, except for some killer whales, I'm told. They have incredible immune systems and are low on intelligence compared to other mammals.
Nuisance concerns: Opossums are prolific breeders, and need places to live. Oftentimes human structures, such as the undersides of porches and sheds provide ideal habitat. Opossums can raid garbage cans and steal pet food. They can also carry parasites and diseases, although rabies incidents are much less frequent than in other animals, such as raccoons. I often encounter opossums living in attics, where they make a terrible mess with their droppings, and a lot of noise. Opossums are also the most common dead animal that I deal with, because they don't live long in the wild, and tend to die under homes and in attics.
 

I woud check with you vet but here is one answer that I found on possum pages:

Opossums are not picky eaters and will consume almost anything, including table scraps and carrion. They do seem to have a particular fondness for cat food, however, especially the tinned varieties. Their normal diet consists of carrion, rodents, insects, frogs, and plants including fruits and grains.