Almost always murmur (if a problem) is due to a structual (mechanical functioning) abnormality of the valve, and rheumatic fever is an abnormal condition that can damage the heart valves.
PTSD can effect the immunity system and cause an individual to be vulnerable to infections Rheumatic fever is an infection and occurs most commonly in childhood and tends to multiple recurrences. Did your sister ever be diagnosed for rheumatic fever. Stress could cause a reoccurence.
Stress can also be a underlying problem for high blood pressure and can damage the heart.