I'm thinking she can magically siphon off or decrease her mass as desired.
This would let her shrink or grow in size, but even at human size she'd still
be nearly a hundred earths in weight. She could also probably fit however
much she wanted to eat in her stomach, which I might make fleshy for the
sake of the vore. This is probably because she's no longer purely a black
hole, but "humanized".
