It was supposed to be an ordinary trip to a music festival. And at first, it was.

"It was a lot of fun," says Valerie Lemus, "I definitely don't understand how people can last all day though."

In spring 2017, she attended the Coachella music festival in California with a couple friends. But first, they stopped at a boutique and purchased what Valerie initially thought of as "hats."

"They were just beautiful, feathered hats. They had amazing patterns. And I bought one… 'cause I thought it fit my outfit perfectly."

Valerie says she received compliments on her outfit all day and only later learned that her "hat" was, in fact, a Native American headdress.

"It was literally the first time in my entire life that I'd ever heard of anything about it being wrong to wear a headdress," she says. "I had no idea that I was being ignorant."

For Cherokee professor and blogger Adrienne Keene, however, Valerie was yet another headdress offender among far too many.

"There are probably hundreds of people or companies or Instagram posters that I have talked to over [the past] six or seven years."

And so, Adrienne did what she's done dozens of times before. She called Valerie out in an post on Instagram.

Four hours later, Valerie says her feed was inundated with critical comments.

"People were saying I was ignorant. People were saying I was racist… I would wake up with this huge feeling on my chest… I was losing sleep over it."

Valerie maintains that she knew nothing about the cultural significance of the headdress, and had no idea it might be problematic for her to wear one. But Adrienne says ignorance is no longer an adequate excuse for cultural appropriation.

"If you search for 'Indian headdress' or 'Native American headdress' online, you'll get links for where you can buy one, but you'll also immediately get links of why you shouldn't wear one."

Not long after Adrienne shared her photo, Valerie deleted the original image and posted a public apology.

"I made a huge mistake," Valerie says.

Adrienne has thanked Valerie for her apology, but Valerie says she still feels upset about the language Adrienne originally used to call her out, saying that she and her fellow headdress-wearing friend would be "dragged all over the internet."

"Why would you want somebody to be dragged all over the internet?" Valerie asks.

For her part, Adrienne insists she had no desire to see Valerie and her friend "dragged", but that she won't acquiesce to tone policing either.

"That anger that I feel — that frustration, that sadness, that pain — is completely justified. So it's hard when someone who is engaging in a practice that is incredibly harmful expects the patience and the kindness, not realizing that she's the fifteenth image that I've seen that day."

Ultimately, however, Adrienne says she was impressed by Valerie's apology.

"I was so grateful," she says. "This does not happen often."

This story originally aired on May 28, 2017