Cressida Wells (née Atkins) is a female Sim who lives in Bridgeport, the neighborhood that ships with The Sims 3: Late Night. She lives with the Cook family as Lady's live-in esthetician. Her bio indicates that Jeffrey and Lady Cook might try to hide their corrupt activities, but she doesn't walk on the glue. She is Hyacinth Atkins' daughter. Her aunt is Violet Atkins. Her cousin is Ryan Atkins, and her cousin once removed is Jett Atkins - Ryan's son. She has a part-time job at the spa. She has 1 point in the guitar skill.
She is good friends with Emmy Starr and Elspeth Cook, distant friends with her mother and acquaintances with Lil Bling. She dislikes Jeffrey Cook and Lady Cook. The fact that her surname differs from her mother's implies that she has either changed her name or was married at some point in her life. It could also mean she got the name of her 'father' even though there is no known father in her family tree.
Even if she is related to Jett Atkins, it is possible for the two to start a romantic relationship because they don't see each other as family.