Ughhh shop it yourself then

Took a curbside order out to a lady. Here is the conversation.

Customer: I tried to add items to my order and it wouldn't let me. Me: Was the order already done being shopped? Customer: Yes Me: you can't add items to an order already shopped. You would have to make another order. Customer: Its not my fault you guys shopped the order so fast that I couldn't add the items.... At this point I realize I am talking to the same lady that would complain if I shopped her order to slow and I feel my annoyance rising on the inside. Me with a fake smile in response: ma'am where would you like me to put your order?

WTF