This is where I think I'd disagree. I think we've basically convinced her to cut her losses, as far as she's concerned. I doubt she'd be receptive to haggling under the best of circumstances, let alone after the rather animated discussion we just had. She's none too kindly disposed towards either of us. About the only leverage I think we have that she won't be able to argue her way around is free repairs, and even then, we'd basically be charging her for her 'free' work. That wouldn't go over too well.
Besides, we've already got something extra out of this; we've made a new friend. And kept her out of trouble that she doesn't deserve. That's good enough for me.
Plus, if we start pressing her for more money, it'll look like we really DID have an angle for ourselves after all, and that might be an issue if we ever find work with her friends. I doubt she'll have much good to say about us.
Long story short, I say we take the 40, be glad that we got Momoka off the hook, and call it a day.