You've probably read Amanda's post. If not, take a moment and do so. I'll wait.
Yes, a blast cell was found, and yes, it probably means remission is no more, but nothing is definite. Amanda is having a biopsy right now and will not have results until Friday.
Her blood-counts as a whole, however, are higher than they've been since any of this crazy crap started. Blasts, from what I've read, do exist in normal healthy people, just not in large numbers. And that's why nothing is definite: it's possible that one of these random rogues was detected, and that she's fine.
Either way, she's scheduled for another round of chemo next week, and the biopsy results will help the medical team decide how best to proceed.