cheating-is-good

Best answer as chosen by Asker / Ratings
Okay, so there are people blocking the entrance to the Gym in Blackthorn city? I cannot really remember but if I am right, then if you fly to Goldenrod City, and go to the Radio Tower you will see that it has been taken over by Team Rocket! So what you need to do is train your Pokemon for the last gym, while you take out the Team Rocket members at the same time. Once you beat all the Team Rocket members in Goldenrod City's Radio Tower fly back to Blackthorn City and check the Gym. If you defeated them all, then the people will have moved and you can fight Clair. I would suggest using Ice Pokemon because she uses Dragon types, you will have an advantage over her.

Hope this helps. :)