They mention at one point that her blood can be almost euphoric to have, addictive and such. I imagine the FL fears the idea of being eaten alive quite literally, but not so much eating the flesh as eating the blood. Yes, it's a liquid so you technically drink it, but this seems to be a play with words much like vampires feeding off blood. They drink it, but they are also eating it. She is very much afraid he will devour all her blood and kill her, as apparently he did in the original story. This seems to be a tale of the FL taming the monster ML and giving him a heart.