Character Analysis
Clear as Mud
Crystal is Ben's daughter with Diondra, all grow'd up. Ben wanted to name his daughter Krissi. Is "Crystal" Diondra's compromise? We're not sure. We're also not sure what Crystal's last name is. Diondra has been living under the pseudonym "Polly Palm," so maybe she's Crystal Palm.
There's a lot we don't know about Crystal. She and her mom are "best friends" (33.10). They're so close that Diondra has told Crystal that she murdered a girl, and Crystal protects her mother. Libby, having dealt with her fair share of murder, sympathizes: "What does it do to a girl who knows her mother is a murderer?" (40.29).
Libby also feels close to Crystal because they look so similar. Although Libby turns Diondra in to the cops, she doesn't turn in Crystal, even though Crystal is the one who actually attacked her. After the rest of Libby's family has been taken away, maybe it's nice to meet a family member she didn't even know existed.
In addition to the family resemblance, Crystal really wants to meet her dad. "He's my hero" (33.18), she says. Maybe because Libby now knows Ben is mostly innocent, she lets Crystal go free: she knows that's what Ben wants. It's Libby's way of paying him back. After all, she gave a false testimony that helped put him in jail. It's the least she could do.