I agree that summer houses are generally not a good place to store valuable things. You could hire a person who could sometimes visit it for maintenance; but still, they are usually vacant. Besides, your neighborhood also tends to consist of many other summer houses that are also vacant during off season. Perhaps the best thing you could do is to have a contract with a security system that is directly connected to security guards or the police. I am afraid that a car would not be a good place to store valuable things, either.... A car is to be driven (away). I heartily hope that she would come up with better measures so that she won't be threatened any longer.