Stuff the case with crumpled newspaper for a while, change it every couple of days. I then sprayed mine with Lysol spray really heavily and let it sit outside on a blistering sunny day and repeated that for 2 or 3 days. Seems to have worked pretty well for me. Others have used odoreaters or some other form of charcoal and one of the deodorant soaps, Dial? maybe.
Once Bitsy smells good you will love her....well, you already do don't you?