Don't focus on doing the pattern so much. You don't want her to just forget you're up there and start doing the pattern herself. She needs to listen to your cues, not just make some circles. Like Harlee says, do arena work. Before you do anything, make she is conditioned though. I do a lot lengthening and shortening strides. I lope circles, asking him to lengthen and strenthen at the four "points" of the circle. I don't know about other people, but I do a lot of dressage exercises with him too. These are PHENOMENAL for helping barrel horses. All sorts of lateral work, bending,pivoting, haunches in flexing, collecting, and I sometimes through in groundpoles. You want to keep them fresh, so only ride the barrels a few times a week or maybe once a ride. Do walk to lope transistions without the barrels. Make your horse change from all gaits normally. Once she can do all this, then work on the barrels. If you just keep walking her in a cloverleaf, she's going to hate it fast.
Hope that helped.