you still don’t make any sense…unless you are leaving out more details. You can only add the speeds of the two cars together if they hit while going the complete opposite direction. Unless your grandma too lost control and hit the truck coming the in the opposing lane then NO is it not comparable. Sounds like your grandma was going 35mph when a truck going 47 t-boned her… NOT a force of 82mph. Its just a 47mph crash