Niknik is good people around here, so I like to give her the benefit of the doubt, but I was kinda torn on her complaints as well.
The rudeness and the fact that the manager admitted the girl was rude and did nothing about it are legit concerns.
Me personally, when I get that customer that is particular about each item on their plate and breaks it down for me, it's just my luck that it's the customer I'm going to make mistakes with. I never make mistakes with the carefree people
Groupon/Restaurant.com/Etc. are all pretty well-known for sometimes messing up or not being available once you go to use them, so I don't think I'd ever only bring a certain amount without backup money.. or I'd at least never order more than I know I can afford without the coupon.