She made her stage debut at the theatre while still a student in a production of Viktor Pelevin's 1993 allegorical story The Yellow Arrow in 2011.

Since joining the Ugala, Sepp has appeared in roles in productions of such varied international authors and playwrights as: George Stiles, Fyodor Dostoyevsky, Abi Morgan, Carlo Goldoni, Rainer Werner Fassbinder, Ken Ludwig, and L. Frank Baum, among others.

Roles at the Ugala in works by Estonian authors and playwrights include those of: Tõnu Õnnepalu, Martin Algus, Oskar Luts, and A. H.

Sepp's impersonations included Renārs Kaupers of Brainstorm, Brigitte Bardot, the Spice Girls, David Bowie, Jennifer Hudson, and Anne Veski, among others.

[13][14] On 3 August 2019, Sepp married Jaan Jaago, guitarist and vocalist of the Estonian folk band Curly Strings.