Is she an abused dog?

It is not your job to do an abuse investigation...BUT if I were you, I would take the dog next time I saw it on my property, and call the proper authorities. If she has no colllar and tags, she would be considered a stray and they will take her in. Check first if your area has a good shelter that can offer medical and behavioral care and assure a good shot at adoption! I suspect if it was me, I would end up with another dog. Don't know what your situation is, but if you are unable to take it, maybe you can start networking to see if anyone would want to foster or adopt. Good luck, you are a good person, with a big heart!