Closed mitral valvotomy is perhaps the most commonly done heart operation in India. When done well and in well-chosen patients, the results are very good for many years when the women could get married and have uneventful pregnancies and deliveries.
It is however true that a mitral valve damaged by rheumatic disease does not become normal after closed valvotomy; a certain percentage of valves will undergo further damage over the years in spite of prophylactic injections of penicillin every three weeks. If a hundred patients do well in the year of the operation, only 70 of them may remain free from symptoms after ten years. When symptoms do appear, the patient may need valvotomy again or valve replacement as an open heart procedure.
Since your sisters breathing `is not like that of a normal person' three years after valvotomy, she should undergo a cardiac evaluation without delay. Tests, especially echocardiography, will reveal the present condition of the mitral valve and whether any intervention is needed. Until she is examined and her heart status is determined, it would be premature to discuss her future plans.