I agree with Indigo that there are two issues at play.
As far as whether to help her figure out how to avoid making mistakes, I don't know that I'd spend a lot of time on it right now if I were you. If anything, I might ask "have you thought about ways you might reduce the silly mistakes? what have you tried?" and go from there. Have been trying really hard to ask my kids how they might go about solving something before teaching them how I have done so myself.
For the top student thing, I might just reassure her that she has tremendous value no matter her place in the class and that sometimes she will be the top student and other times she won't be in that spot.
How challenged is she in school? I'm wondering if the material is so far beneath her that she has too much time on her hands and thus is challenging herself with these perfectionism and competitiveness patterns. I would worry that she may not want to try new things if they might not lead to a perfect score or top position. For us, that's what led to really pushing the school for acceleration (single, now double subject). We didn't want the kids to get caught up in a 100% with little effort mentality. They were heading there...
