Ti, I'm so, so, so sorry to hear that. You can be sure your Harley girl will be in my thoughts.
"Heart murmur" is a broad term. A heart murmur can be just a very slight flaw in the valve that allows some leakage back into the connecting chamber in the heart, or it can be more serious. Talk to your vet at length and find out how serious it is. You may need - or want - to have some tests run so you can determine how best to keep Harley at optimum health. Keeping her nutrition tops is going to be so important for her long term health, but I don't know that I'd depend on a vet for advice in that area. The vast majority don't have much knowledge about animal nutrition other than to recommend Science Diet or Eukanuba . . . and you know all about those from the discussions here!
Keep us posted on Harley's condition. We're with you!