like what @Chaves said it's a mental image.
i believe it's like how zoro uses imagination to create asura with his aura, she does the same to create the demonio with her flower petals.
her ability is not limited only to her body parts, as she showcased the ability to create clothes before, and she can even control color.
i think her ability is like cracker's ability, where he can create everything out of biscuits, and i think she can uses flower petals to create anything she want (though it consumes stamina), she was only doing it with her body parts because it's easy to imagine/familiar with, and didn't have enough mastery of her DF.
i believe it's like how zoro uses imagination to create asura with his aura, she does the same to create the demonio with her flower petals.
her ability is not limited only to her body parts, as she showcased the ability to create clothes before, and she can even control color.
i think her ability is like cracker's ability, where he can create everything out of biscuits, and i think she can uses flower petals to create anything she want (though it consumes stamina), she was only doing it with her body parts because it's easy to imagine/familiar with, and didn't have enough mastery of her DF.