It took me 6 months to train Syd.
For us it was all about doing it on her terms. We first tried to outdoor train her...but it was winter...so it was too cold and windy for her.
So then we tried pee-pads...but she would still sneak off into a corner to go.
So finally we moved the pee-pad into one of the corners she was sneaking off into...and bingo! We've been good ever since.
Apparently she doesn't like people to watch her go potty and she wanted a private place. So now she has her own private bathroom in our kitchen in a spot under the counter where there used to be a dishwasher but now is just a space.
We don't have any accidents unless the pee-pad is too dirty...in which case her highness refuses to use it.
Don't get discouraged...it will come.