I wish you had mentioned the nameplate rating of that electric oven. The ones I've installed have been wired at 40-amp, 240-volt (much more than a vacuum). Anyway, my personal opinion is that you did the design work on this one, you should be responsible for it. The only way I see that you could have saved yourself on this one is if you had agreed in advance that you didn't think it would work, but you were willing to try it as an experiment at her expense.
Dave
