Pamela suffers from a rare disorder in which three distinct personalities exist, each dominating at different times. The condition Pamela is suffering from is called

The condition Pamela is suffering from is called Multiple Personality

Explanation:

Multiple Personality is a dissociative disorder in which two or more personality exist in an individual. This individual manifest multiple actions leading to others not been able to understand them.

For example, an individual who is relatively quiet and humble and at same time exhibited a more playful and mischievous personality. And, also, the individual manifest more mature and confident personality.