Hitchhiker
We hate to break it to this person, but that probably was not your grandmother, it was just a wild coincidence that this old lady looked just like your grandma. But it could have been another sign from the universe that it was trying to help you deal with this great loss.
If we have learned anything at all, it is that nothing really makes any sense in life and absolutely anything can happen at any given time. With that being said, who knows, maybe this was the long-lost sister of this person’s grandmother, who just happened to be on the side of the road.