The correct answer is: dissociative identity disorder.
Step-by-step explanation
Donna exhibits two separate personalities, each well-defined and distinct from one another, so she is diagnosed with dissociative identity disorder. This type of disorder is characterized by at least two separate personalities, that randomly appear, but there could be more.
Moreover, it is a psychological condition mostly caused by a trauma during childhood. For example, in most cases it appears when the person has suffered abuse in his/her childhood.