Hi, full disclosure - I work at PrestaShop.
I've just stumbled upon this thread, and I'm glad that we're listed in the least worst eCommerce platforms
I just wanted to point out - for those hesitating because of the complexity of hosting the solution yourself - that we are releasing a 100% free, hosted version of PrestaShop (and it is hosted on good, optimized for PrestaShop servers too).
This is still in beta, and you can register here: http://www.prestashop.com/en/beta (don't worry, access is granted quickly).
We should go out of beta in a few weeks.
@algorythmics: Whatever solution you choose, best of luck to your wife!