The answer should be $1.15 if I counted correctly.
To solve this problem, you first need to know how much the total cost for her lunch was. You can calculate this by substracting the money that she received in change ($0.63) from the money she gave to pay($10).
$10 - $0.63 = $9.37
Since her lunch cost included the lunch special cost ($7.75), the sale tax ($0.47) and the cost of her drink, all you need to do is substract those $7.75 and $0.47 from the total lunch cost. The answer you get is the cost from your drink.
$9.37 - $7.75 - $0.47 = $1.15