Jackie frequently experiences intrusive memories of an emotionally traumatic experience, which she has been trying to forget. Her intrusive memories provide evidence of unsuccessful

repression

Explanation:

Repression: In psychology, the term repression is considered to be one of the defense mechanisms which was proposed by one of the most influential psychologist named Sigmund Freud.

The term repression refers to the process of an individual's psychological attempt to direct his or her impulses or desires towards any pleasurable instincts through discarding them from his or her consciousness and keeping them in the unconscious. Through repression, an individual excludes the distressing thoughts, feelings, and memories from the conscious mind.

In the question above, the statement signifies the process of repression.