Isabelle,
I'll try to fill you in on some details. Firstly, the Aquitania was not a sister-ship to the Maurerania being much larger (and slower). She was built more as a Cunard answer to the White Star "Olympic" Class and the upcoming "Ballin" trio being planned/built in Germany (these became Berengaria, Leviathan and Majestic after WW1). Mauretania's very near sister was the Lusitania - lost in WW1. I have heard that the Mauretania model on the QE2 might have some Lusitania "bits" on it but I must research this some more.
Cheers!