I am dying my Nans hair for her tonight, last time I dyed to way too blonde and it made her look grey so I've bought a medium ash blonde to put over it. Will this work as she has the light blonde dye on her hair still from last time? Also I know some of you will say tell her to go to a hairdresser but she is almost 80 and can't afford to she also doesn't have the confidence to do this when I offer to pay for her to. So please can you just advise if this will work as I don't want to make her go ginger or something lol. Thanks in advance girls xx