The invisible represents shyness.

She is all those who prefer to stay on the sidelines rather than expose themselves.

Shyness (also called diffidence) is the feeling of apprehension, lack of comfort, or awkwardness especially when a person is around other people. This commonly occurs in new situations or with unfamiliar people; a shy person may simply opt to avoid these situations. Although shyness can be a characteristic of people who have low self-esteem, the primary defining characteristic of shyness is a fear of what other people will think of a person's behavior. This fear of negative reactions such as being laughed at, humiliated or patronized, criticized or rejected can cause a shy person to retreat. Stronger forms of shyness can be referred to as social anxiety or social phobia.