Cribbing can originate for many reasons. It can be inherited (or learned from the Mom), but often occurs from boredom or is learned from other horses. However, it can also begin from intestinal discomfort and ulcers, or a mild cribber can become a serious cribber after some digestive issues become a problem. So, in this case, the first thing I would look at is the function of her digestive tract. How is her stool? Check the color and texture–is it dry, wet, hard, soft? How is her appetite when she does eat? How much water does she drink, how does she behave after eating–any sign of discomfort? All these are good detail questions to ask when looking at a case from the holistic perspective.
If the digestive health appears poor, supplements like probiotics, prebiotics and supplements to improve hindgut health all are beneficial (https://shop.harmanyequine.com/product-category/digestive-support/).
Treatment of cribbers can be very tough. For many, just having them outside in a field with company is enough to stop the cribbing. Keeping a horse in a stall much of time leads to boredom and increases stress, which increases cribbing. From a Chinese perspective, stress affects the Liver acupuncture meridian, which then overheats and “cooks” the Stomach and Spleen meridians, leading to ulcers. So, decreasing stress is important. I have used the herbal formula APF to combat stress and have had a number of horses reduce their cribbing. Sometimes the Bach Flowers (http://www.homeopathyworks.com/section.php?xSec=68), especially Rescue Remedy®, can help relieve stress and change the emotional state enough to help the horse cope with her life.
Other cases need more specific and stronger treatments. Acupuncture is frequently beneficial. Herbal supplements can be very helpful to heal ulcers. Many natural products contain antacids, which can decrease the absorption of important minerals such as Calcium, Selenium and Manganese. It is best to use herbal products without antacid additives. One of my favorites is made by Hilton Herbs (http://www.hiltonherbsusa.com/products/digest-support-previously-gastrix/469). For many serious cases, Chinese herbal formulas are stronger and can be very helpful, but do need to be prescribed by a vet with training in Chinese herbs since there are many variations of formulas (http://www.tcvm.com, http://www.ivas.org, http://www.aava.org/search/ ––all of these organizations have trained vets).
Horses with confirmed behavioral issues that seem to have good digestive health can be treated with homeopathic medicine. Homeopathy is a very powerful form of medicine with many remedies that can be used to treat mental conditions. To treat a complex case such as this one likely is, it is best to work with a homeopathic veterinarian (http://www.theavh.org). Many detailed questions need to be answered to come up with the right remedy that can really help correct this behavior.
Unfortunately there are quite a few horses who have become such confirmed cribbers that nothing seems to help. You have to learn to manage them, as you have done by feeding her in the one place she will eat. Usually over time she will improve some or you figure how best to manage her. If I had to pick one management thing that works the best, it is turn out in as large a pasture as possible with a buddy or a herd. If she still cribs on the fences, the addition of and electric wire to the top can help save the fence.