The Sacrificial Daughter

My sister and I both have congenital heart disease, but only one donor heart. Parents decided on Tomb-Sweeping Day, whoever reached the mountain top first would get the heart. Parents favored me, giving me a head start. I struggled, reached the summit, but fog reset me to the foot. My sister's social media post showed she got the heart. I died trying to reach the summit. My soul saw my sister with a new heart. I returned to the day of the climb.