For this idea you will need a dictionary (Usual English-English)
The idea is to mark with highliging marker all words which you can use to describe her.
Example: lovely, kind, good looking, etc.

Then with your girlfriend you can read these worlds and have fun and ask her to do the same. Of course you will need some more time to do it, but then you will be rewarded.
Also you can write some interesting love quotes on dictionary margins.