Hi! I feel like this parent is just being rude. In our school/class we don't have a snack time...so for birthdays it is a cupcake at lunchtime only. There is no party. We may take the cupcakes to recess with us if time is running short. Just tell her. Our schedule continues and most of the time I always say no cupcakes anyway because the kids will eat the icing and throw the cake away. Then they are wild for the rest of the day...glad recess is after lunch. Don't be afraid to let her know that a cake is too much and cookies or a dessert at lunchtime or your snack time is all the time you have and that you cannot have a "party". We're only allowed two such "parties" a year. Good luck!