I remember the episode where the doctor takes Rose to witness the end of Earth.

Lady Cassandra O'Brien.Δ17 brings an "ipod" (a jukebox) and plays "classical" music.

But I can't remember what song it was? I for some reason think it's "toxic" by Britney Spears but not 100% sure?

It's very likely that I'm misremembering because (in my head) Toxic is Cassandra's theme song?