To be honest if you don't mind eating CS for every meal you and your daughter can eat 3 CS meals a day for less than the $80 the QSDP will cost you for just getting 2 meals.
Breakfast CS meal runs around $8 and lunch and dinner CS with drink runs around $12. That is $32 each per day and that covers all 3 meals not just the 2 that you will get if you buy the quick service dining plan.
Now there are some CS meals out there you can seek out like at WPE that may cost you over $15 and then it might break even having the QSDP but for most CS meals they run $12 or less. If you add a dessert then you can add $3 or $4 more. But for us, if we aren't on the FREE dining pan where you get the dessert with each meal we would never order dessert. We never do no matter where we eat so we prefer to not have them on vacation. It helps minimize the weight we will gain on vacation.