Karla, have you tried cat food? Most dogs just love cat food. The other thing you might try is baby food veal. That is yummy stuff to critters and very soft and easy to digest. She might lick it off a spoon if you hold it!!
(It's ok to feed cat food to dogs, but cats shouldn't eat just dog food, because it doesn't have a couple of key ingredients cats need. )
It is so hard to watch our beloved pets age so quickly, especially when they're fine one minute and not the next. My prayers are with you and Susie. I have a 95 lb. black lab named Guinness. Or, as my friends call her "Labzilla"