Complex sentence: Her last performance with Nightwish was recorded on the live album/DVD "End of an Era"; after the show, the other members announced to Turunen that she was no longer a member of Nightwish.
Split into simpler sentences: Her last performance with Nightwish was during a concert recorded for the live album/DVD "End of an Era". After the concert, the other members informed Turunen that she was no longer a member of Nightwish.