What should I do about the situation?.?

Well there is nothing the grandma can do about it first off, yes she can ***** and complain but the school board knows that you were picked for a reason and they will be confident in you. With the girl, most likely you both will get over this reason that you are not liked she is still young and holds grudges like a little kid. She will have grown up and matured when she gets into high school with you. Most people get over their childhood immaturitys, so I don't think you will actually have to worry about this situation. Remember things change over time. Good luck and I hope I helped.