Nellie Bly (mispelled in captions as Nelly Bly) was an American journalist, industrialist, inventor, and charity worker who was widely known for her record-breaking trip around the world in 72 days, in emulation of Jules Verne's fictional character Phileas Fogg, and an exposé in which she worked undercover to report on a mental institution from within.
She is mentioned by Xavier during an interstitial segment that happens between I Am Jackie Robinson and I Am Anna Pavlova when he is racing Berby through time. After taking her train, Berby and then Xavier are seen passing a girl in a hat who is being photographed.
Although there is no direct mention of who she is, this is implied to be her based on context and matches what she historically was famous for wearing.
Given her being photographed, this likely happened sometime between 1889 and 1890 when she completed her 72 day global circumnavigation.
Nellie Bly was actually her pen name. She was born Elizabeth Jane Cochran in 1864 and changed her name to Elizabeth Cochran Seaman when she married Robert Seaman in 1895.