I think this is a training issue not a racing issue, she made it clear that something in her training with Siri wasn't right. I think this awakens her to her Kona prep and maybe some changes need to be made going into Kona this year to defend her title.
So I find it interesting that in the blog just prior, her San Juan 70.3 report, she comments about how she didn't have "months to prepare" for that race. The St. George race was only 6 weeks later. It takes 6 weeks to really see a good effect from a training block, and I'd be willing to bet she didn't spend the last 6 weeks trying to peak for this race.
I don't think it's so much that something "wasn't right" with her training with Siri. It's not back to teh drawing board, it's just back to regularly scheduled training IMO.