I have an older kitty with a heart murmur. It was discovered a couple of years ago at an annual checkup, so since it wasn't there before, they recommended me to get the ultrasound. I did and they rated Marius's heart murmur a grade 3. The vet told me that as long as he's acting normal and feeling ok, that I needn't do anything but keep an eye on it. Over the past couple of years, I've checked with my vet to see if I needed to do another ultrasound, but he said that it seems to be staying the same, so it's still just a matter of observing. So far he seems to be doing ok, so as long as nothing changes (eating habits, litterbox habits, water intake, activity...etc) I don't need to do anything.
I would think that if your kitty is acting normal, then you could probably wait it out. It could be a good idea to get the ultrasound (I don't think they use anesthesia for this one, but I could be mistaken) just to get a grade, but other than that, you could probably just observe her to see if anything changes in her behavior/habits. I believe they treat high grade heart murmurs with medications, so hopefully neither of our babies will require it.

Do let us know how she's doing.

**hugs**