It happens. I don't think it had anything to do with offering food after 6 days, though.
If it happens again, try to encourage her to strike again by doing the mouse/rat dance with the dead rat held in a pair of tongs a few inches away from her nose. Sometimes they will stop eating if it doesn't "feel" right to them. I have a couple of snakes that will absolutely not eat unless they strike the rat square on the nose.
Good luck!