If it was departing the west coast it would be easy. Its much rougher from the east coast as the FAs are overnighting in order to work the return flight the next day so there are no extra crew in BOS. I'm still trying to figure out how they scraped up an extra FA is such a short time. I assume they would have had to fly one in from the west coast on another airline or they found a spare in one of the other east coast cities (maybe FA spending a few extra days for vacation?) and flew them on another airline up to BOS.