Answer:
Isolation.
Step-by-step explanation:
Psychosocial theory of development was the theory theorized by Erik Erikson divide into eight-stages of development from infancy to adulthood.
Erik proposed that successful completion of each stage leads to healthy personality development.
The stage at which Sherri is in, in the given question is intimacy v. isolation.
This stage occurs at the age of 20 to 40 years. This stage involves building intimate and loving relationships with others.
Sherri, who is struggling to find a long-term and stable relationship is at this stage of intimacy v. isolation. Since she is not able to build intimate relationships she is going through the crisis of isolation.
So, the correct answer is isolation.