That may or may not be true, however there are a lot of things that you can do to keep her comfortable.
I would not rule out prescription medication.
Most heart murmurs in small dogs are benign (especially seniors).
Often it is age related.
If the condition was concerning I am sure your veterinarian would have recommended medication or referred you to a specialist.
Most supplements are scams and are a waste of money.
Any symptoms?
Most of my small breeds had heart murmurs, asymptomatic, no treatment required.
