for starters, why is "natural" good? and why are these powders not "natural"?
she'll probably have trouble formulating a good response. Mostly because there isnt one. Asorbic acid (vitamin C) is Asorbic acid. It doesnt matter if it was synthesized in lab. At all. They are the same. The means of transport can make a huge difference in how it is absorbed by the body.
The ingredients aren't unnatural at all if they are things found in food. Whey protein concentrate is equivilant to most orange juices that you probably drink, it probably isnt just oranges squeezed. The way it is introduced into the body is what may or may not be effective.
There is a big advantage to using nutritional supps. Many needs are not met by food, or at least without large quantities. If you were going to get 1g of protein per pound bodyweight like many suggest, you would probably ingest a large amount of fat and have trouble finding room for all the other foods you need.
Many post workout drinks also include a quick absorbing monosacharide (single sugar). Table sugar is sucrose (a di-, meaning two simple sugars joined together), so to get the same effect of say Surge, you would have to quickly ingest something in a large quantity like say, corn syrup (glucose), and very quickly eat a sizeable quantity of extremely lean meat. I think most would agree that Surge wins out.
The supps. are far from needed, but they can help you get the nutrients you need without creating a tough to follow diet. Many powders also include many trace minerals that are essentially removed from today's over processed foods. Granted, many fight for the same receptor sites so they dont have as strong of an effect. A lot of today's foods are what is actually unnatural.
Overprocessed junk is easier to find and cheaper than good wholesome foods. If she has stopped at a fast food restaurant within 6 months, then she should at least try something that could benefit her in some way.