Christy Vanderbel is a former friend of Penny's from Nebraska, played by Brooke D'Orsay. She appears in "The Dumpling Paradox".
Christy was engaged to Penny's Cousin while she was sleeping with Randall, so Penny considers her as "kind of family". She stays with Penny during the episode and hooks up with Howard, strengthening Penny's description of her as someone who sleeps around. Indeed, Penny recounts Christy's list of every guy in Omaha she slept with, which she jokes is just a list of every guy in Omaha. She also agrees with Sheldon that she is the "whore of Omaha".
Christy inadvertently drives Penny out of her own apartment when she hooks up with Howard in her bedroom, and the two upset her by abusing her personal belongings, such as using her robe, her loofah mitt and getting her stuffed bear collection sweaty.
Although she displays signs of affection towards Howard, Christy is highly materialistic, and goes out with him only on condition he buy her stuff and take her shopping. She dumps and breaks up with him when she confronts Howard's mother Debbie Wolowitz, who threatens to cut Howard out of the will, as long as he keeps going out with her. She also publicly claims to everyone how Howard is her "first Jew".
Despite not appearing in "The Conjugal Conjecture", she is mentioned by Randall, her brother at Leonard and Penny's Wedding II.