Betty de Famme is a magician who is the trick behind her twin sister Bonny de Famme's teleportation magic trick. She holds an intense dislike of the young magician Trucy Wright, alongside whom she appeared in the magic show "Trucy in Gramarye-Land" at the Penrose Theater. She appeared as a witness in Trucy Wright's trial for the murder of Mr. Reus.
Betty, her twin sister Bonny, and Mr. Reus were chosen by Take-2 TV producer Roger Retinz to appear as Trucy Wright's co-stars in the magic show "Trucy in Gramarye-Land". However, Retinz then asked them to participate in a prank on Wright during the show's dress rehearsal at the Penrose Theater. Due to her jealousy of Wright's skill at magic despite her young age, Betty quickly agreed to help with the prank and roped her reluctant sister, who was a huge fan of Wright's, into it.
The plan was to have Wright make a fool of herself on live television by having Mr. Reus fall out of a coffin that Wright would stab with a rubber sword during the show, after which he would pretend to be dead. Bonny was to remain on the stage and prevent Wright from getting hurt during the prank, while Betty would hide in the understage area and use a remote control to activate the winch suspending a dragon set piece over the stage, thereby causing the set piece to fall down. Mr. Reus was connected to the same wire as the dragon set piece; once Wright went into a panic over his apparent death, he would "come back to life" and fly up into the air, causing everyone to have a laugh at Wright's expense.
Although the prank initially worked as planned, things quickly went wrong when Mr. Reus somehow turned up dead afterwards, having been killed by a stab wound to the back. As Wright's sword trick involved replacing a sharp steel sword with a fake rubber one before stabbing it into the coffin, it appeared to everyone watching as if she had failed to switch the swords and actually stabbed Mr. Reus to death inside the coffin. Additionally, since Bonny and Retinz had alibis and Betty's existence was unknown to those not directly involved with the show, Wright was regarded as the only possible suspect and arrested for the crime. During the police's investigation, Betty, convinced that Wright had committed murder, conspired with Retinz to go to any lengths necessary to have her found guilty in court; Retinz promised to use his position as a producer for Take-2 TV to have Wright tried in the court of public opinion, while Betty was to pose as her twin sister in court and testify against Wright.
During Wright's trial the following day, her defense attorney, Apollo Justice, proposed that Mr. Reus had actually been killed in the understage area and his body had been placed in the coffin from below afterwards. Once Betty, in her guise as Bonny, was called to testify, Justice found several holes in her testimony which indicated that she had been in the understage area during the show, proving that there were two Bonnys – as the real one had been on stage – and blowing the twins' cover. After Betty revealed her existence and admitted to being in the understage area, Justice tried to accuse her of the murder, as she was the only one besides Wright to lack an alibi. However, Prosecutor Nahyuta Sahdmadhi then had the twins admit to participating in the defamation plot against Wright, and Betty presented a video which proved Mr. Reus had been in on the prank, disproving Justice's theory that the murder had been committed in the understage area and once again returning suspicion onto Wright. In the subsequent recess, Bonny went to the defendant lobby to try and talk to Justice, but Betty followed her sister and interrupted their conversation, taking Bonny away.
However, Bonny stood up to her sister when court resumed, saying she could no longer remain quiet, and testified in Wright's defense by presenting a video of the magic show filmed by a fan of hers. This new evidence allowed Justice to open up the possibility of a third party stabbing Mr. Reus to death at some point after the dragon set piece fell, and this prolonged the trial long enough for Retinz to take the stand in order to testify about the prank. Justice accused Retinz of the murder and was able to prove his guilt once and for all by showing that he had fabricated an alibi for himself by committing the murder remotely via a sword planted in the stage's catwalk, which had fatally stabbed Mr. Reus (who had actually been a fan called Manov Mistree working for Retinz) when he was pulled upwards after Betty dropped the dragon set piece.
After Wright was acquitted and Retinz arrested for the crime, Betty was horrified that Retinz had made her an unknowing accomplice to murder and blamed herself for Mistree's death, but Wright reassured her that neither she nor Bonny were at fault. Despite now knowing that Wright was innocent, Betty claimed that she still hated her and angrily dragged her sister out of the defendant lobby when Bonny let slip that Betty had once been as big a fan of Wright's as she was, even having asked her for an autograph that she still had to that day. In the aftermath of the trial, Bonny and Betty came to have trouble finding work, as their best known trick relied on Betty's existence remaining a secret and they now found themselves unable to do it. Bonny proposed that they take Wright up on her offer of joining the Wright Anything Agency as magicians, which Betty was violently opposed to.
Betty is a very rude and aggressive individual who often bullies and pushes around her sister. She is also extremely short-tempered, to the point that she was incapable of maintaining her disguise as her sister when under pressure. She also has a difficult time apologizing, regardless of how much she realizes she is at fault, instead getting Bonny to speak for her when making amends. Although genuinely respecting her as a magician, she is extremely jealous of Wright, feeling that she and her sister are unappreciated by the public and prevented from obtaining fame and success, which lead her to agree to what she thought was a prank by Roger Retinz to humiliate her on stage.
However, despite all this, Betty is not a particularly vicious person at heart and felt ashamed when she realized that Wright had been framed and she had been an unknowing accomplice to Mistree's murder.
Her Japanese given name, when combined with her sister's given name, forms the word "Kikimimi" (聞き耳), meaning "ears poised for listening".
When the kanji "na" (菜) and "no" (野) in her surname "Nanano" (菜々野) are removed and reversed, they become "yasai" (野菜), which means "vegetables"; this may be a reference to carrots, which are stereotypically eaten by rabbits.
Her English given name, "Betty", is most noticeably a play on "batty", referencing her costume's bat motif. The name "Betty" is a short form of "Elizabeth", and is commonly associated with the notion of queenly status to the point of purported self-worth, which ties into Betty's self-centred, bratty personality. Betty is also sometimes used as a slang name to refer to a "babe"; an attractive woman, with pejorative connotations. This is likely a purposeful contrast to her sister, Bonny's, own name, which is also used as a slang name for an attractive woman, but with positive connotations.
Her English surname, "de Famme", may be a play on "defame", in reference to the plot against Trucy Wright.
When not pretending to be her sister, Betty generally has more alert and fierce expressions than Bonny. Like her sister, she regularly performs magic tricks when talking with people, but the animals she releases from her hat are purple and black bats with fur that resembles that found on the chest of her costume.
Betty shares a number of similarities to Dahlia Hawthorne: both appear to be gentle and innocent at first, before showing their true colors (although Betty is simply ill-tempered and aggressive rather than murderous); both carry a distinctive parasol; and both have a twinsister who they pose as in court in order to give misleading testimony.