I'm just gonna point point out that if you have to ask question like that, you might as well ask why she's bothering to work at all, when by that same logic she could just do whatever the hell she wants whenever she wants. You might also ask why the humans aren't faitfully and fearfully serving the Abyssals while you are at it, going by that same logic.
Shit like this annoys me to no end when it's brought about shipgirls as well. If you have to ask a question like that then you also have to ask either A) Why are those ghosts even pretending not to be the same as the Abyssals, just with a different paintjob, or B) How does the the war effort get anything done at all when any individual shipgirl can do whatever they want with impunity.
It doesn't even work as a joke. It was stopped being funny around the thirtiet time, by now only the fridge horror remains.