How close should you be? "It's a difficult issue," says Coco Myers, coauthor of The Nanny Book. "You're her partner in caring for your child, but you're also her employer." The trick is to be friendly, but not necessarily become friends.
Whether she works out of your home or in a daycare center, your sitter's bound to pick up tidbits about your personal life. But you don't have to offer all the details -- just what she needs to do her job. For instance, if you're concerned that your daughter may act out in daycare because of the longer hours you'll be putting in at a new job, talk about it, focusing on your daughter, not on your emotions.
How much should you pry into your sitter's life? If, say, her son just started kindergarten, of course you should ask her how it went. But constantly checking in about her dates is crossing the line.
She may insist on chatting you up, however. "Taking care of kids can be lonely work," says Lorraine Caputo, a psychotherapist in New York City. "Sometimes you want an adult to vent to." Show her the same kindness you would a talkative office mate. If it doesn't interfere with your work, or hers, it's fine to be a sympathetic ear once in a while.