But when Becky got in touch with ASOS to challenge their pricing, they defended the decision, she told Metro.co.uk.
"According to ASOS, the price is different because it has a different product code," says Becky.
"When I asked for clarification, they said it was because the design is different. The hem is lower and the neckline is slightly different."
She went on to say:
"I’m not sure why they decided to change the design – are plus size women supposed to be ashamed of their bodies?
"I understand there is an argument for more material but surely the difference between a size 6 and a size 16 is far greater than a 16 and 18. And if that were the case, why are petite clothes not cheaper?"
She also reached out to Boohoo to get clarification, and they got back to her saying they would review their pricing structure.
ASOS has since changed the prices of the dresses to the same price, but Boohoo is yet to follow suit.