Dogs, as a rule, are more resistant to ringworm that people or cats. And if they do get it, it usually happens on the face/ears and does not form the classic circular patter that people get. So, I can't say for sure, but I don't think this is ringworm.
What does often form circular lesions are tick bites. Sometimes after the tick has let go and is not longer there, you will still see a red, slightly raised, circular lesion. Do you have ticks in your area? If you do I would try giving her some Benadryl (send me her weight and I will give you a dose).
The other thing that causes circular lesions are staph infections. They tend to be flat and slightly crusty and can happen for an assortment of reasons. Sometimes they will go away on their own or with a little Neosporin topically, but sometimes they need oral antibitoics.
I hope that helps, but if you have more questions, let me know.
I had done a bit more research and from images online (I know that's not the most accurate way to diagnose anything)- it looks similar to a black fly bite or other bug bite. It's not crusty/ dried out/ etc., not raised at all, and doesn't seem to itch at all. There seems to be a tiny scab in the center (about the size of a pin head).
She is 40 pounds on the nose.
We do have quite a few ticks in our area, but she is short haired and has no hair on her stomach, so I am able to do a general check daily.
Are there any other symptoms that I would notice that would indicate staph?
The main way that we know it is staph is that they usually get dander or crusting in the area.
Any kind of insect bite... tick or fly... should get better with Benadryl. She can have 25mg (regular Benadryl) 1 tablet every 12 hours until it goes away. If it hasn't gone away in 3 days then I would have a vet take a look at it.