I just don't understand why you don't take 2 minutes to talk to her parent. That's the absolute least thing that I would do in this situation. I get that you're nervous to get cps involved, but that's their job. They are there to protect kids and make sure they are being cared for.
You say you are not the only parent that has said something about being concerned about the situation. If multiple parents are concerned, it is time somebody steps up and calls police for a wellness check or CPS. I can understand the difficulty with previous experiences, but wouldn't you feel better knowing everything is ok, and it is being checked out?