Jessica is Patty and Walter's daughter and Joey's older sister. Although an impressive individual, and quite deserving of attention, her whole life she has been overshadowed by Joey. Patty is particularly guilty of ignoring her awesome daughter during her childhood.
Jessica is the only Berglund who doesn't have her own chapter, and thus the only member of the family whose story we never learn directly. We have to rely on other family members' interactions with her to learn about her life.
In fact, we only meet her directly a couple of times: when Patty goes to visit Jessica at her college (a disastrous visit, we might add) and when she greets Richard at her parents' home in Washington, where they spend a few minutes at the kitchen table talking.
Can we expect her to feel free to live whatever life she pleases? Should we envy her escape from the drama when she goes off to college and Joey moves out of the house? Or is she imprisoned by her desire to finally receive some recognition from her parents? The best evidence we have might be to look at her later opinions of her parents: in particular the phone calls with Richard, when they discuss her relationship with Patty. How has she been affected by her past?