She had over one million followers on her Instagram account and was considered a social media influencer.
Actor and talkshow host James Corden said the news was "incredibly sad" and tweeted to Tomlinson that he is "not on your own in this". Currently, The Sun says the young woman's death is being classified as "unexplained" by authorities, pending a full autopsy and toxicology test.
Felicite and Louis lost their mum Johannah to leukemia back in 2016.
American singer-songwriter Charlie Puth said he is sending "prayers" to Tomlinson and added: "I can't imagine how hard it is right now".
A spokesperson for the Met said: "Police were called by the London Ambulance Service at 12.52pm to a residential address in SW5".
Family pictures show the singer with his fours sisters who have been supporting each other through hard times following the death of their mother.
Louis has cancelled his appearance on tonight's Comic Relief following the tragedy.
Following her death, Tomlinson released the song Just Hold On - his debut solo single - in her honour, and he performed it on the X Factor just days later.