The So You Think You Can Dance host went on a Twitter rant on Sunday after her "awful" restaurant experience

Following Cat Deeley’s outburst on Twitter targeted toward L.A. restaurant TOMGEORGE, an etiquette coach is weighing in on whether or not it’s ever okay to not leave a tip for a server.

The So You Think You Can Dance host, 40, posted multiple tweets on Sunday telling users to not go to the restaurant and that her experience was “absolutely awful.” Her posts went on for hours and included multiple tweets with a vague description of what exactly happened — a situation you should never put yourself in, says Modern Etiquette Coach Maggie Oldham.

“I think what she did, trying to make the restaurant look bad, is actually making her look bad and it’s terrible etiquette to air your grievances like this in a public forum especially when the restaurant is trying to make amends,” Oldham tells PEOPLE. “It sounds like the server did his job, he waited on her, he brought her food, he did his best by comping part of her meal and make amends for whatever grievance she had toward the restaurant. So I think in this situation it was terribly rude of her.”

After a number of tweets, the restaurant server responded to Deeley, writing: “Cat, as your server at TomGeorge I am hurt by your response to free food. I gave you respect, and I served you with love,” along with a photo of her signed bill with a line drawn through the space for a tip.

“With this scenario, we don’t know the full story and so it’s really hard to say whether or not she was doing the right thing, but what I would say is it sounds like it was really the manager and the food that she had an issue with and not directly with the server,” Oldham says. “In that case, by stiffing the server, she’s hurting no one but the server. She’s not hurting the manager who she thinks wronged her in the situation. She’s not hurting the chef if she didn’t like the food. She’s especially hurting the server.”

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“And I think to not tip somebody at all, the only time I would ever say that that’s okay is if the server was extremely, extremely aggressive toward you or rude toward you and it doesn’t sound like this was the case,” she continues.

Deeley responded to the server on Twitter, making it clear it was not his fault for her poor experience: “The food was terrible and your manager was unhelpful and rude. Respect and love should be shown to all, attention to detail is necessary too!,” she wrote, adding: “And as I respectfully told you, the catalogue of errors were not your fault. However the mistakes were repeatedly not correctly rectified.”

Oldham says tipping is especially important in the U.S., where servers often make below the minimum wage with the expectation that tips will make up for what would be their hourly rate.

“Tipping etiquette for a sit-down restaurant where you have servers waiting on you is 15 to 20 percent,” she says. “So 15 percent is on the low end so the service was basic or even a little subpar and anything over 20 percent would be on the high end.”

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Even if a meal was comped, such as in Deeley’s situation, you still want to tip on the full amount of the meal.

“Groupon is a big thing, Gilt City is a big thing where you get a discounted meal with a coupon — you still want to tip on the full amount before applying the coupon,” Oldham says. “The server is doing the work for the full amount of the meal. Same with celebrities — servers are still putting in the work for whatever that bill came out to before it was comped. Celebrities especially should be tipping more.”

A rep for Deeley has not yet responded for comment.