There are no foods that will prevent shedding, but there are a number of high quality foods that will support the skin better...which is about all you can expect a food to do.
It's common for dogs to have an intolerance (not necessarily an allergy) to some grains such as wheat, soy, sorghum. The holistic foods use rice, oatmeal and barley, which most dogs seem to tolerate better.
But, grain-free foods would be the best for dogs with dry skin. They typically have a greater volume of higher quality essential fatty acids, which will contribute to a supple skin. Supple skin holds a coat better than dry skin.
I've never been a fan of Science Diet which, in my opinion, is on a par with grocery brands. I would recommend grain free formulations from quality manufacturers such as: Earthborn, Wellness, Merrick, Canidae, Nature's Variety, Blue Buffalo, etc.
You can't make a mistake with any one of those. The differences from brand to brand are largely marketing, not science. If you compare ingredient panels, you'll see the same ingredients but in a different order.
Next you have to look at the treats she's getting. Discontinue people food such as bread, English muffins, bagels, pasta, cereals...all that grain-based stuff. Next look at your store-bought treats. Don't feed those that contain wheat. If you feed biscuits, there are wheat-free and grain-free biscuits on the market.
If you live in a climate where you have the heat on this time of year, the dry air will contribute to the problem. A supplement such as salmon oil or some other fish oil will be helpful. Most dogs will just lap it up, otherwise you can mix it with their food.
Shedding is largely a natural function of variations in the photoperiod and fluctuations in temperature; and dogs are constantly going from bright to dark places and from warm to cold. That will also contribute to shedding to a certain degree.