The gases inside her gut want to expand outward while lard under her skin wants to collapse in on itself. The inward force balances itself out with the outward, thus making a contained explosion, like our sun, which is pretty big. In theory she could become the size of a red giant star. Which is just big enough to be used as a bowling ball by Gurren Lagann to hurtle at the Spiral Nemesis forces. I haven't totally worked out the math yet, but in theory she could be turned into Magnatar star if we feed her enough tacos and donuts.