Tell her:
1. It's better than getting ****ed down the pub every night.
2. Gaming is a bigger industry than Hollywood movies.
Alternatively, if she likes puzzle games, get her a Nintendo DS with some games, and then when she's hooked, call her a gaming addict.
I've been gaming since I was 10, and I'd rather be doing something interactive than passively sitting in front of a TV vegetating in front of some reality TV nonsense or Eastenders. Watching TV puts your brain into "passive mode", whereas gaming is much more active, like reading a book and using your imagination.