Jansen was sixteen when she joined Apocalypse (the name of the band After Forever in its early days) in 1997. Three years later the band released its first album, Prison of Desire. Floor's ability to sing both classical and rock music have made her reasonably popular in the metal scene.[citation needed]

She has taken sole charge of After Forever's lyrics and vocal melodies since the departure of Mark Jansen in 2002.[1] Prior to this, up until the Decipher album, the two would write together.

Floor started studying music at the Dutch Rock academy in 1999 and entered the conservatory three years later. She studied Theatrical Music and sang many arias from Operas. Later on, she started teaching performing in her own course called Wanna be a Star?!. Her dream is to sing in a musical theater.

Three albums by the Dutch composer and multi-instrumentalist Arjen Anthony Lucassen include guest vocals from Floor. She sang one song on Universal Migrator Part 1: The Dream Sequencer, made a number of contributions to the Star One project and has been confirmed as a guest singer on the next, Ayreon album, 01011001.