Well, If you had asked this question in a couple months, I may have a better answer for you.
But, I AM in the process of toilet training (For a human toilet) my two cats, ages 3 years and
5 years. The older is a girl, the younger is a boy, both fixed from 6 months or so old.
They are doing really well.. An adult cat CAN BE TRAINED to use the toilet.
Just show her where the toilet is. I've found that technique to work in the past with litter boxes so a toilet should be no different. Just set her down on the seat. She will take it from there.
All about Cats http://cats.about.com/
Video Training http://in.youtube.com/watch?v=6oqcigDrezI
Cat Toilet Training Review http://cattrainingsecrets.net/cattoilettraining/