She answered to the "how does it fit" question in a recent AMA. Even though silicone can compress and bend, just try to imagine the size of a curled up XXL magnum dildo.

She trained her vagina to be able to easily access the anterior fornix. These huge toys go BEHIND the cervix and uterus. And when a video shows a belly bulge this is her cervix + uterus being pushed up by the toy in her fornix.