OTOH, it's a little tempting to stay in, just to see how the plot plays out.

Sounds good to me - since you're apparently 'in', I'm curious to see
what happens. I would have backed out as soon as she raised the price.
If 20 minutes of "time to do the math" was BAD for you in the first
deal, think about how much time she'll have to do math before you're
done with furniture repairs, etc. If you stay in, write up and have
her sign lots more receipts, contracts, etc so at least you'll have
something to show in small claims court the next time she does math.
Andy