[Z]

I assume the reason for having a sing off was because they knew Cher would be struggling for votes but they were hoping she would beat Mary, in the likely event that she didn't, they added the bottom two because they've clearly got a big name signed up to do a duet with Cher in the final. That's the only reason that makes sense to me. I hesitate to call it a fix, because to be honest, I think Mary had run her course and Cher had more to offer as a contestant, but I think it's a shame for Mary because she's a lovely woman who deserved it more than Cher (by virtue of being older and Cher having a whole future ahead of her to make it in the music business) :/