Go to a craft store and make a pretty wedding basket!
New: Something small that she can pin to her dress - a small gold or silver heart, bought from the same store.
Old: An old picture of her, perhaps?
Borrowed: This would be the most difficult category. You will all need to put your heads together and think of something you own that she could wear on her wedding day. A bit of lace to tie to the bottom of her dress…something like that.