She May Have Light Fingers
You might not want to think about it, but not everyone in the world is totally, completely honest. Maids may be no more likely to steal from their employers than anyone else, but those who are so inclined have a unique opportunity to exercise their light-fingered tendencies. Cleaning service complaint sites are littered with anecdotes about maids disappearing with everything from lingerie to cash. When someone comes into your home and takes something without permission, it's a violation. You should feel safe where you live, and when circumstances show you that you're not, the frustration and bad faith can cost a lot more than the item that was taken. Stick with a cleaning service that uses dedicated employees, not subcontractors, and bonds them. You might also want to take the extra step of always having someone at home on cleaning day.