A 54-year-old Aboriginal woman from a remote community presents to a fly-in GP clinic with exertional dyspnoea and ankle swelling. She had acute rheumatic fever as a child. Echocardiography organised by the visiting cardiology service shows severe rheumatic mitral regurgitation and pulmonary hypertension. She has been lost to follow-up and has not received benzathine penicillin for several years. According to Australian RHD guidelines, what is the highest priority long-term intervention in addition to managing her heart failure?