We know the girls didn't ride there.
But if I were a worried grandmother, trying to imagine where on earth my young granddaughters were... I think one of the possibilities that would go through my mind would be that they set off to see their mama/auntie who was working not so very far away.
I think I would come up with all sorts of scenarios, many of them unrealistic because I wouldn't want to think of darker possibilities.
BBM - and w/all due respect to you and Gma, IMHO, I believe I would have simply picked up my telephone to find the answer to that question... that's just my guess only, of course...