Ummm so she wanted to spit in their food BEFORE they got the check and wrote the supposed note with no tip?
Hadn't they already eaten at that point?
I get the impression that when the family thought the hostess said "Dan" and Dayna was their waitress, they made the comment about being surprised (because of misunderstanding the HOSTESS) and Dayna took it to mean more than it did. JMO!