For her to remember you is good advise, but I wouldn't send flowers or the like. You don't want her to believe you are desperate. If you are still friends and see eachother then remind her verbally. For example if you are talking about movies then bring up a funny story that happened when you watched a movie together. (do you remember that one time when we watched...?) make sure the story is funny for her. Nothing that embarrasses her. Do that here and there and she will remember how much fun you guys had together and will miss you.
The key to anyone missing you is for them to remember you. Send her friend flowers, yellow and orange colored daisies or tulips. Let her know you still care but are okay being friends. This will be key to rekindling any feelings she might still have. If she doesn't respond, move on.
Probably the best thing that you could do to make your ex girl friend miss you is send her chocolates, greeting card or the most important thing thing that you remembered you gave her that she really likes the most.