I'm so very sorry for your loss. How extremely sad. Please accept my condolences. <3
And as nearly everyone else said, there is no "correct" prescribed thing to do in cases like this. Do what will give you comfort and ease and meaning, w/the knowledge that she would have probably known immediately why you picked that specific option.
I buried my guy with several very specific things, one very very traditional (Mizpah coin, dating back to our first days of couple-dom & given us as gift by my delighted conspiring bro & his wife.)) and some others possibly a bit outre' sounding to those who wouldn't have known the history. Since they never found out anyway, screw 'em
Trust yourself on this. One suggestion, maybe: If you should decide to leave a letter, a pic, a song, or suchlike -- you may wish to keep an exact copy of it for yourself as well. Sometimes that's comforting
Chyia PS & yeah, that's one of the things that's going to be buried w/me: the other half of the Mizpah coin. I don't care if it's soppy, **** off