A 4-year-old girl from Delhi presents on day 5 of illness with fever, cough, and a widespread maculopapular rash. Her parents report she had high fever (40°C) for 3 days, followed by rash onset. On examination, the rash is confluent on the face and upper trunk, with some blanching. She has cervical lymphadenopathy and hepatosplenomegaly. Her hemoglobin is 10.2 g/dL and platelet count is 80,000/μL. She was vaccinated with MMR at 12 months. What is the most likely complication she is at risk for?