Final answer:
Mary displays the ego-defense mechanism of regression by exhibiting behaviors associated with a more immature stage when faced with the anxieties uncovered during psychoanalysis.
Step-by-step explanation:
The ego-defense mechanism that Mary displays, as described in the sentence "As the psychoanalysis progressed she presented infantile features; a precarious identity, strong affective dependence, dissociation, and self-destructive work related behavior," is likely regression. The defense mechanism of regression is when an individual, faced with stress or anxiety, returns to a more immature behavioral stage. This reversion to childlike patterns of behavior demonstrates an attempt by the ego to defend itself against feelings of anxiety or difficulty coping with the pressures of adult life.