Her pizza has 12 slices and she ate 1/2 of the pizza for lunch so that leaves 12/2 = <<12/2=6>>6 slices left
She eats 1/3 of the pizza for dinner, so she eats 1/3*6 = <<1/3*6=2>>2 slices
She had 6 slices and ate 2 slices, so that leaves her with 6-2 = <<6-2=4>>4 slices for tomorrow's lunch
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