Forgetting someone takes time, the longer you've known her, the
longer it takes.
Perhaps try engaging yourself in some activities, or set yourself
some medium-term targets to keep yourself focused on other
things.
I once read somewhere that if you keep reminding yourself to
forget, you won't be able to do so since you have to remember to
forget, which is in itself an irony.
Rather, let time run its course. Sooner or later, she will be in
your subconcious. 
