platinum that has gone gray

I am trying to go platinum and I just switched stylists because my friend was doing my hair and she left it too yellow. So the new girl that has been doing my hair said it is normal for platinums to go through a gray stage. My hair is gray in some spots and underneath my hair it is getting dark gray. She guarantees me it will wash out as the toner washes out but I'm nervous that what she is saying isn't true. She says that toning it can make it gray. Please help.