Head spots and white markings like that are usually pure white. These are more like splotches that are diluted. I'm still guessing she's merle hooded. Lovethoseratties, try googling the coloration "merle rat" and see if that looks like your girl. I'm sure there are other terms or similar coloration close to merle too. But her markings are definitely hooded, with the coloration of (blue?) merle? Or maybe pearl merle?