I agree about not giving her the card back.
I think it's one of two things. Either, as has already been said, you're saying the "look at the great times you're throwing away", or you're saying the sarcastic "I guess none of it meant anything, huh beeotch..".
Either way, it's an attempt to get to her, and it'll show her that you're still brooding about it all. Which of course you are, that's natural, but the point is for your own respect, she doesn't need to know.
As for her stuff, when my last major ex dumped me, I had some of her sh*t at my place. I kept it for two months (honestly, I was hoping she might come round and we could 'talk' ..euurrghhhh..). Then after two months I figured she obviously didn't want it back and gave it to a charity shop.
Do what you want to do. If you want shot of it, drop it off at her place when you know she won't be in. Short note "Here's your stuff, nice knowing you. Bye." Gets it over and done with, no attempt made to talk to her, gets her properly out of your life. Yeah, I say do it. This is the way to go.
bp1974