Selection in Jawahar Navodaya Vidyalaya (JNV) mainly depends on district-wise cutoff, number of seats, difficulty level of the paper, and category. For a Rural General category student from Beed district, 78.75 marks is a good score, but JNV cutoffs usually go quite high because seats are limited. In many districts, General category cutoffs range around 80–85+ marks, though this can vary each year. so, selection is possible but not guaranteed. Your sister has a fair chance, especially if the paper was tough this year, but final confirmation will depend on Beed district’s cutoff and merit list.