A mother’s reaction when a shopkeeper said her 13-year-old daughter should wear Spanx could teach a lot of people something.

The daughter was trying on a dress, at the request of her mother Megan Naramore Harris, for an upcoming formal dance.

The Kansas mother and daughter took to Dillard’s to try on dresses, and after she tried on the dress, a staff member said she should wear Spanx to flatten her figure.

When Harris said her daughter did not need to wear a body shaper, the shop assistant then told her they thought otherwise.

So Harris decided to hit back with an open letter on Facebook.

In it, she talks about body shaming, and how, what may have been an up-sale, could potentially be damaging to young girls anywhere.

“I wish I had told you how many girls suffer from poor self-image, and telling them they need something to make them perfect can be very damaging,” Harris wrote on her Facebook page.

She added: “My daughter is tall, she swims, runs, dances and does yoga. She’s fit. She’s beautiful. She did not need you telling her that she is not perfect.”

Harris signed off, saying: “Mother of a beautiful girl.”

The empowering post, written last month, went viral, and was shared hundreds of thousands of times.

In a second post, she added: “People have said that I should be ashamed for embarrassing my daughter.

“First, I ONLY posted this with permission from my daughter! It was her choice. Second, please know I do not want this lady fired!”

Speaking to local news station KAKE after the incident, Harris elaborated, saying: “The entire conversation I had with the sales lady, I will NOT repeat, but I can ASSURE you it was not a basic up-sale. I have been in sales before and know the difference between a pushy sales person trying to make a sale and someone who has gone beyond the point of being rude.”

But Dillard’s said they had taken the criticism on board.

A statement read: “At Dillard’s, our mission is to help people feel good about themselves by enhancing the natural beauty found in all of us. We train our sales associates with the goal of creating a completely positive experience with each visit.

“It is certainly never our intent to offend our customers. We have reached out to this customer and her daughter, and we appreciate the outreach of so many of our followers and customers to bring this issue to our attention.”