I Have A Neighbor Who Is Fostering Her Granddaughter. The

I have a neighbor who is fostering her granddaughter. the child is 25 months. about a month ago while babysitting I noticed a blistery looking rash on her genitals. I mentioned it to her grandmother who said it was diaper rash and not a big deal. However it has gotten worse. When I said it didn't look like diaper rash to me, she told me it was genital herpes and that she got it from her mother. The grandmother told me she had genital herpes and it was no big deal, she took medication for it. However when I mentioned taking the child into her doctor I got a shrug and was told when things were less hectic she would get around to it. I am concerned. What are the health risks to the child? The child has acted as though it bothered her, but grandmother says no, I am imagining it. What should I do?