As much as I am appalled by those learn tarot in 3 minutes type of book, I was given The 2-hour Tarot Tutor by Wilma Carroll ISBN 0-7499-2610-4, and was quite taken with it. It is a good thorough intuitive approach. If your Gran wants to be reading by September then, if she follows the book's instructions, she will indeed be reading by September. And good luck to her!
My Dad, who will soon be 85 introduced me to tarot in the '70's .. so I'm all for our elderlies getting into it. Moreover, she has a lifetime of wisdom to deepen anything she learns.
mythos