I think taking AP and IB classes/tests helped me, not only in getting through college quicker (saving me money), but simply preparing me for college. I was shocked at the kinds of things my friend's never had to do that were natural to me by that point - namely writing longer papers.
I had no trouble getting into law school, and I never heard of someone not getting into a graduate school because they had AP credits, rather than a specific college class.
I don't think there is one single error. I think it was a combination of things that sunk that campaign, from not skipping to Iowa to not being able to deal with other caucus states to not being able to handle a protracted campaign, etc. It was a strategic failure of epic proportions.
I think even her war vote could have been dealt with had she run a completely different campaign.