Other contemporary diary entries/letters, admittedly written by men NOT originally from the area, also spell it as "Bluett," and I even have run across one mention of the bridge that was either written at the time (or later transcribed) as "Blueck's," but as you point out, phonetics are funny that way -- particularly nineteenth century phonetics.
If the Blewett family were prominent, and more importantly, if we knew they held any land along that stretch of the creek, I'd climb out on a short limb and say you're onto something!
(You ought to see the spelling variants on "Luxapalila" in those letters home!!)