From the Super Mario Wiki
Sarah Barnard was the wife of scientist Michael Faraday. They married on June 12, 1821, sometime after meeting in a church, and stayed married until Faraday's death in 1867. They had no children. In Mario's Time Machine, she meets Mario after he travels back in time to London in 1831 to return Faraday's Magnet after it was stolen by a time-traveling Bowser.
Mario's Time Machine
According to Mario's Time Machine, Sarah Barnard lived in London in 1831 with her husband. When Mario first meets her, he asks her if she has ever met Michael Faraday, and she replies that she is, in fact, married to him. She also says that this year marks their ten-year anniversary after marrying in 1821 and that he also invented the electric motor that same year. Mario, astounded, asks what he has done with this motor, but Sarah says that his motor has proved thus far to be impractical for actual work. As a result, Faraday is attempting to discover a way of generating continuous electrical currents, allowing for the creation of a practical electric motor. Mario then asks if Faraday discovered electricity, and Barnard replies that both him and his mentor, Humphry Davy, have both considerably studied electricity, and she then gives a book that documents some of Davy's lectures, Conversations on Chemistry. Mario asks her who Humphry Davy is, and she explains that he introduced Faraday to the field of science after Faraday sent him a notebook based on Davy's lectures, although Davy died two years ago in 1829. Davy made Faraday his apprentice, and as Faraday was only an uneducated bookbinder, he greatly appreciated the opportunity; however, Davy then voted against Faraday becoming a member of the Royal Society, which Barnard speculates is because he was jealous of Faraday's success. She then mentions that she wants to bake a cake for her husband, but she has run out of chocolate. Mario then brings her some Chocolate, and she thanks him. She then continues talking about Faraday and how he was never once angry with Davy, as he had given him his scientific career. Mario then asks about what happened with the Royal Society, and Sarah explains that, despite Davy's opposing vote, Faraday became a member of the society. She says that it was a great honor for him, but also that, in his "box of awards," he wrote that the happiest and most important date to him was June 12, 1821 - the day he married Sarah Barnard.