I had that problem myself once, what really helped was:
- having friends that understood my need to grief (i.e. not push me)
- doing lots of activities with new people to get him off my mind
- and it might sound silly, but I actually performed my own kind of ritual to say goodbye: wrote a lot of letters that were never sent-read by anyone else, did drawings, listened to music that reminded me of him, then on a fixed date in the calendar, decided for myself that it was time to move on.
- another thing that helped me was discussing with my friends why I wasn't with that guy anymore (there is a reason why it doesn't work out!) I made a list of things I didn't like about him and made a list of things I'd like for a new relationship. That put it all in focus and not long after that I was already starting to think about another guy.
- if she can afford it, she could buy new clothes or new accessories to make her feel beautiful and "in the game" again..when she is ready of course.