It may or may not be ringworm, but her skin is so bad that I would about bet she has lice and a Vitamin A deficiency, too.
I really doubt ringworm, but since it is only a few spots, I would play it safe and get some 'Captan Powder'. It is a garden fungicide that you get at a garden center. You add water and remember to shake it up good any time you use it. Just 'dabble' it on the spots. You can do it in the winter by just using it locally.
If you get in horses with skin problems like lice and rain rot, you should get a bottle of injectable Vitamin A. It is available anywhere supplies or feed are sold for cattle. DO NOT inject it; just squirt 5 cc into any horse's mouth. You can keep Vitamin A levels up by using it weekly for 3 or 4 doses until the rain rot and lice disappear or green grass is available. It will prevent rain rot by just giving a dose once or twice a month. Or, you can give the oral dose a couple of times while you get them started on a good supplement that is high in Vitamin A like 'Farnam's Mare Plus'.