Serana doesn't use Ice Spike

[maanfall]

So, in a new game I rushed dawnguard. I was level 4 or something when I first encountered Serana. In the beginning I didn't pay any mind to her not using ice spike because I thought she would just learn it at level 12. But now I'm level 22 and she still hasn't used ice spike once. Then I thought that because I rushed DG some obscure bug occured for her not learning it correctly, but according to the CK she has already learned it: http://i.imgur.com/3bD7tcd.png

As far as I know, I don't have any mods that alter Serana in any way. Does anyone know how to fix this? Many thanks in advance