If your horse is scared of saddles, you've got a lot of work in your hands before you can even think about barrels.
As Toto said, make sure your saddle fits her and she doesn't have chiropractic issues. If there is pain behind anything, of course she's going to refuse.
If pain is not causing it, then you can work on retraining her. If she's scared of being saddled, then you need to go back to ground work. Act as if she is unbroke and never did any of this before.
I also agree that you should be working with a trainer because it sounds like you need help with your horse.
Get your horse broke,broke, broke first. Green broke and barrel training does not go together.
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