I highly recommend checkers, chess and sudoku (you can start with 4 squares until she gets the hang of it).

If I were in your shoes I would pick something you know she is good at and then just keep bumping up the age level until you hit a level where she actually starts to slow down a touch. Not necessarily to the so frustrated that she gives up, but just has to actually think a bit. I went through this with Wolf starting school this year...