"I chose to pose like that.. no one told me to do anything," she said Wednesday after posting the cover on Instagram.
Social media users had suggested that Graham was instructed to place her hand on her leg in an attempt to make her appear slimmer.
Others pointed out that Hadid's arm looked Photoshopped.
"I find it so interesting that the ONE plus size model they include in this picture is covering half of her own leg with her arm," one person wrote.
"Hey Vogue, great job on including Ashley Graham on your cover, but did she really have to cover her thigh w/ her hand? #notsosubtlebodyshame," another added on Twitter.
Graham herself celebrated the cover, writing, "Dream. Come. True! THANK YOU @voguemagazine."
She discussed the importance of size diversity in the accompanying interview.
"Sixty-seven percent of the women in America wear a size 14 or larger. Sixty-seven percent. Maybe you could ignore those consumers before, but now, thanks to social media, they're making their voices heard," she said.
"And what they want is to be visible."
Graham is known for her modeling work with Lane Bryant, and became the first plus-size model to appear on the cover of the Sports Illustrated swimsuit issue in 2016.
She shared a photo of her cellulite and a body-positive message on Instagram in January.
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