This is Nicky.
She is not a very emotional being. She never cries, NEVER! But this is a different case.
All of her life she felt unhappy and lonely even though she had family and friends around her who loved her very much and cared for her. The problem was that she couldn't find her meaning, her purpose in life.
This moment represents her finding out what that "purpose" is. She gets so overwhelmed and excited about it so she sheds a few happy tears.
-Mangup.