What would you have done in this woman's place?

Imagine you're a single mom and have finally found an au-pair to take care of your kid so you can work again. But the girl abuses her position of power by "forgetting" to do 50% of her work, by damaging your possessions in?voluntarily, by using your phone/internet & running up high bills, without apologizing or offering damages.
It happened this year to the family I worked for as an au-pair once, too. The mom talked and talked to this girl instead of sending her back to France as some of us advised her. She was just too afraid of not being able to find another one & thus lose her own job.
What would you have done in this mom's place with no family around to fill in? Would you have suffered the impertinence of a 19 year old girl for a whole year? And do you think this is a question of self-confidence/fear? I sometimes feel the mom lacks self confidence and is too afraid of setting limits to people who take advantage of her, even though finding an au-pair is quite difficult. Thanks.

You're all right, and I told her about the same thing, but
a) the family lives in a rural area where not many au-pairs want to go, it's not like here in Munich
b) the kid is in school for about 5 hours a day and the au-pair just needed to work 2 or 3 hours to help in the house
c) agencies in Germany charge up to 600 $ for an au-pair even if the girl leaves after a few days. That single mom couldn't afford that.

I still think she should have put her in her place.

Without question, this girl would have been shown the door within seconds of this starting. The 'Mom' should have immediately called some Au Pair service for a replacement - even if the one she had did not come from them. In the meantime, if she could afford an Au Pair, then she certainly could have afforded day-care.
It would seem that the 'Mom' struggles, and really has no one to turn to at times of crisis, which is a shame, and my heart goes out to her. But she really needed to put her foot down straight away on this, no if's and's or but's about it.

i'd have taken it out of her a.ss!

As I understand it you typically get au-pairs through an agency. I would talk with that agency and told them the problems and ask them to address them. If that doesn't fix it....then ask for her to be removed and send a new one. You often can find some intermediate care to take care of your children while you search for someone full time. Your children are too important to leave with someone who doesn't care for your possessions.

I definetely would have fired her! then I would find a reputable day care in the area while I worked until I find another replacement. There are plenty of fine day cares that take very good care of children of all ages. If I could not find a day care for whatever reason, I would either take a leave of absence or resign even if it meant use up savings for a little while while i found replacement. My children come first.
I would not trust someone that irresponsible and careless with my children.

I would have fired her and sent her back. She would have been lucky if she didn't have to pay for the damages.

Oftentimes, people will not spend too much money on childcare, so people take advantage. However, if the mom wasn't happy and was being taken advantage of, that is a breach of contract. she was too timid to put the girl in her place so that is her problem.