First of all I would like to clear the title; when I say "lose" I mean it in the way you may lose your headsets or your glasses on the bus.
While I was playing a reached a way that I could only access by jumping, so she could not follow me immediately, so as usually, she(like any other ally) will make the way around and disappear for later on coming back to you.
It did not happen this time. She did not show up a couple of hours of gameplay later(not all the hours at ones

She is not on the Jarls castle or on the last place I saw her. Could she be dead? Or lost somewhere on Skyrim?
Thank you very much.