The pair let themselves go on 14 chicken pieces, six bags of fries and large cokes after driving to a KFC outlet in West Yorkshire.
They spent an hour and a half scoffing the 5,456-calorie feast. The mega bucket, which busts the Health Department's recommended 1,940-a-day calorie count for women, cost her £13.16p.
Days later regular customer Natalie got the fine in the post for breaking the restaurant car park's 75-minute limit, The Sun reported.
Natalie insisted: "It didn't feel like I was in there all that long. We were hungry."
The 24-year-old, who eats at KFC three times a week, fumed: "It's disgusting. I spend a lot of money in there. Now I'm never going back." Natalie complained to restaurant bosses that she was unaware of signs warning of the time limit.
KFC said Monday restaurant parking was contracted to private firm Civil Enforcement Ltd — but promised to review Natalie's case.
A spokesman said: "A parking restriction was introduced to prevent non-KFC customers using the car park.
"The 75-minute time limit is designed to accommodate our customers who generally eat for about 30 minutes."