steeking! you can indeed cut it but it takes some bravery and a sewing machine. Find the point where you want to cut the scarf, and place a marker on the knitting. Go a few stitches to the left of this and place a marker and do the same to the right. from these left and right markers you will need to sew with your machine a line straight down. This gives you a sort of tram line where you want to be cutting. once you have sewn those lines take a sharp pair of scissors and cut the scarf at the point you marked. ta-da! you now have two scarves.
Now if tis was me i would pick up stitches along the cut ends and knit a decorate border of some sort to hide the cut part.
For more information about taking a scissor to your work, have a look at this thread
, it is focusing on sweaters but the basic techniques apply.