Body Language
Make sure your body language is friendly & open, turn your body towards her direction, feet, face and all, and then without doing anything else, just get back to what you were doing.

When a girl looks at you, acknowledge her gaze for as long as you can. But, instead of looking for too long… be the one to look away first.
Smile
Give her a warm and confident smile while she is looking at you. This will show your confidence.
