Those sound like times she could be with you? Eating lunch together, having quiet time or reading together. Maybe she is afraid youre going away too. Can you just keep her closer to you for a while and see if that helps? Cuz it sounds like she is old enough to understand that she shouldnt go outside without letting you know. Is the time-out away from you (in a bedroom) or near you (on a naughty step or stool near you)?