Jessica and Rachel realized that their quest to save Leonard's life would involve making his previous attorney look sloppy, so Jessica decided to subpoena her and get her on the stand. 

She did admit negligence, but she also made it crystal clear that she believed Leonard was guilty. This sent shock waves through the case, but Rachel had Mike to help her out. 

She and Mike went to see the victim's father and realized he was lying about not knowing the drug addict. The next day, Jessica owned him on the stand, thus securing Leonard's exit from prison. 

In flashbacks, we got to see Jessica bickering with her father over her choice of career and it made her realize that she wanted to help people. 

Sutter turned the shareholders of PSL's biggest customer against them and it forced Harvey to work without Jessica to save the firm. He managed it, with help from Stu and Louis. 

The Leonard case gave Jessica the guts to let the team know that she was leaving the firm and moving on. 

She went to see Jeff and he said she could go with him. The two cuties kissed it out on the door step.