Mums, if you find an usual number of men's numbers in your helper's diary, is this something you would worry about? How would you investigate? Or would you just question her?

I don't think there is something to worry about, but ya you can be more careful in observing her behavior (again, it depends how long she is working with you.) Personally, I respect the privacy of others. Agreed with others regarding an investigation, having CCTV installed would be great idea.