"They didn't say a reason why - they were quite rude to my partner," she added.
"I think its disgusting because there's more and more people becoming vegan and vegetarian these days," she added.
The couple ended up going "elsewhere for food" and ended up having fish and chips for dinner.
She said she felt "as though we vegetarians and vegans don't mean anything to them" and suggested KFC should put a sign up letting them know they had no options for them.
"I'm not going to KFC ever again," the woman said.
A KFC spokesperson told Devon Live it was a shame the customer had left disappointed.
"We never want our fans to leave feeling disappointed. It's always amazing to see how popular our Original Recipe Vegan Burger is, but due to less demand from people out and about at the start of this year, and our focus on running our restaurants responsibly with smaller teams, we prioritised the vegan burger in areas where it was a massive hit," the spokesperson explained.
"We're sorry this guest wasn't able to get their hands on one."