You want to reduce the tension by initiating a friendly conversation about something that you can both see and agree on. The minute you say, “Look at your cool red shoes!” or “Are those pants blue?” the little one will follow your gaze down. The child now has something comfortable to look at besides your scary stranger face while she gets used to your presence and voice.
Don’t compliment the child directly. Go for what they are wearing or holding. You’re looking to bring positive focus to something personal, but not so personal that you run the risk of making her more self-conscious.