She was remorseless, but she lacked method.

Sophie and Howl were living - somewhat quarrelsomely it must be confessed, although they were said to be happiest that way - in the moving castle again

By now it was clear that Howl was in a mood to produce green slime any second. Sophie hurriedly put her sewing away. "I'll make some hot buttered toast," she said. "Is that all you can do in the face of tragedy??" Howl asked. "Make toast!

More about Howl? Sophie thought desperately. I have to blacken his name! Her mind was such a blank that for a second it actually seemed to her that Howl had no faults at all. How stupid! 'Well, he's fickle, careless, selfish, and hysterical,' she said. 'Half the time I think he doesn't care what happens to anyone as long as he's alright--but then I find out how awfully kind he's been to someone. Then I think he's kind just when it suits him--only then I find out he undercharges poor people. I don't know, Your Majesty. He's a mess.

You are a terror, aren't you? Leave this yard alone. I know just where everything is in it, and I won't be able to find the things I need for my transport spells if you tidy them up.'
So there was probably a bundle of souls or a box of chewed hearts somewhere out here, Sophie thought. She felt really thwarted. ‘Tidying up is what I’m here for!’ she shouted at Howl.
‘Then you must think of a new meaning for your life,’ Howl said.

A fickle heart is the only constant in this world