Well.... you gotta start somewhere, right?
What did you do for your warm-up? Was she listening to you in the warm-up pen?
The pattern aside, I think probably the biggest mistake I see is that you didn't MAKE her listen to you. Even when my horses are in a new environment, I don't really care if they gawk at things, but I expect them to keep their attention and respect on me.
Now it will certainly depend on the rules of the show that you attend, but if the rules allowed it, I would have made her circle that second barrel several times instead of just allowing her to "miss" it. You gave yourself a no time anyway for breaking the pattern; why not turn it into some schooling instead? (Again, if the show allows it ... some don't.)
And then as I mentioned about the warm-up, I do lots of bending, flexing, and giving exercises in the warm-up pen; especially if they are a young horse in a new place. Even though things are new and exciting around them, I want their attention on ME and listening to my cues.