Sarah ~ If course we'll keep you and Callie in our prayers. But, please don't worry so. Callie will probably be around for many, many years.
Did the vet rank the murmur? Our vet told us that they are given a number - from 1 to 6 -- 6 being the worst. Our Pepper is a 6. No medication will help. Unless they come up with a kitty heart transplant.....

But, Pepper is going strong after 3 years. She's never been sick. She plays until she exhausts us all. She leaps to the top of doors, climbs shower curtains, jumped off the 2nd floor balcony, tangled with a cat 3 times her size and won (20-pound "Princess" has never shown herself in our yard since being smacked by 6-pound Pepper). So, keep the faith. There is hope.