Rivers have been historically excellent natural borders, so crossing a wide and deep river on their journey to find their promised land away from hostile nations is a good decision. Especially not building a bridge is good, it will make it hard for any heavily-armed pursuers trying to hunt her.
Maybe I've been binging this manga too fast but it feels like everything has been fairly fast paced so far. I was surprised to know it's been a year already since she first celebrated her birthday in the old village.