Wild River is purely fictional. The plot and characters were invented by the author or creators to entertain and engage the audience. There's no real-life basis for it.
I'm not sure specifically as I don't know this particular 'the river wild indian story'. It could be about the adventures of Indians near a wild river, like their hunting, fishing, or how they interact with the nature around the river.
The girl might be associated with the grille as a symbol of discovery. She could be the one who first notices the grille and its importance. In a dalive story, it could lead to a hidden treasure or a long - lost secret. Maybe she finds an old key that fits the grille - locked door, and behind it is a room full of ancient artifacts.
Since I don't know the story well, it could be a young Indian brave who is on a journey along the river. Maybe an old shaman who has a deep connection with the river and its spirits.