SAT Barista

A barista pulls three grande beverages: a latte (2 oz. espresso, 14 oz. milk), a triple latte (3 oz. espresso, 13 oz. milk), and a soy latte (2 oz. espresso, 14 oz. soy milk). The barista's a little hungover, though, and forgets which drink gets the 1 oz. of whip; she randomly chooses a drink to which to add the whipped cream, and furthermore forgets to label the cups. A lactose-intolerant customer, who will have digestive problems if she ingests more than 13 oz. of dairy product in a short time, randomly chooses and consumes one of the three beverages. What is the probability that the customer will soon be headed for the restroom?