Cornhuskers ointment will help with the cracking on her thumb. My girl's (2)seemed to suck on their thumbs close to bed time to help we would place a sock over the apporiate hand (we called it the thumb sock) it was just part of getting ready for bed get your jamies on and don't forget the thumb sock. As far as putting substances on the thumb during waking hours not so sucessiful as it is an unconcissous thing you just need to be consistent (not mean) bring it to their attention tell her to take her thumb out of her mouth. Be prepaired you will have to say this at least 10k times. welcome to the joys of parenthood.