Is she a reptile person? Does she keep any of her own? Because you could buy her a young snake or other reptile and slip it on the critter, then present it to her. There's also a cute commercial where a guy puts the ring on a new kitten's collar. Had a teacher in high school who proposed to his girlfriend by running string all through the house and the yard and as she followed/pulled the string she finally came to a ring tied on the end. I thought that was cute too, and definitely memorable.