The complainer, whose profile says she is from in Lisbon in Portugal, posted the scathing review, which said there were no tables available, despite it being a busy weekend.
User tinkerbell_pt said she was turned away at 12:30pm on September 24.
She wrote: "We showed up at 12:30pm and asked if they had a table for two. The waiter gave us a 'uh' attitude and whilst they checked their book we looked around and more than half of the restaurant was empty.
"We got turned away with a 'sorry, no tables available, only one outside at 2pm' excuse. I can only assume they weren't in the mood to receive our money."
The restaurant is rated sixth best in Margate and has been nominated for a Kent Tourism Award.
Many diners have given it five star reviews, with one recent comment saying it was 'good, pleasant, unfussy, attentive service - just perfect'.
Owners Nadine and Simon Morriss hit back at the woman, calling her review 'unfair' and claiming the reviewer just wanted to 'get revenge'.
They said: "It is always disappointing to receive negative reviews especially when ourselves and the team work so hard to deliver great food and service.
"However, such is the nature of TripAdvisor and we can always improve from constructive and honest feedback.
"To receive a negative review for this is simply unfair, you are not 'advising' future diners about your experience of our restaurant, you have simply vented your anger and tried to get revenge for us not having a table available for you immediately when you have strolled in on a busy, sunny weekend without a reservation.
"As you said yourself we were already half full at 12.30, 30 minutes into our lunch service where we had 80 covers booked in, with advanced and staggered bookings throughout the afternoon.
"Our trained and experienced restaurant staff do not expect to have to explain what we mean by 'sorry we do not have a table available until 2pm' to customers who have not booked but would have happily shown you our reservations diary had you asked for clarification.
"For your information, we had lots of lovely customers book in for later tables, go off for a walk on the beach and a drink and return an hour later for an enjoyable lunch.
"Sorry that you felt the need to rate your experience as 'terrible' and we hope that leaving this review made you feel better."