Dorothy Skerrit

 was Nikola Tesla's secretary sometime around the 1900s.

Before Dorothy met Nikola Tesla she wanted her own career, "something steady". Tesla showed her all the discoveries that could be made. At first, they seemed like impossible things for her, but by the 1900s she considered her new life as something normal, steady.

She was present, when Nikola Tesla presented Niagara Generator to potential investors. Dorothy met the Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yasmin Khan and helped them defeat the Skithra. (TV: Nikola Tesla's Night of Terror)

Behind the scenes
Dorothy Skerrit was indeed one of Tesla's secretaries in the real world. However, the two did not meet until 1912, potentially several years after the episode's setting, though the exact year is never made clear within the episode.