Why she would have done this, we'll never know, but crossing the river would also explain why Ted Mead found footprints on both the North and Eastern banks of the Arthur River. Maybe the river is not as brutal down stream in winter as suggested.
Given that all the remains have been found relatively close together, perhaps she never had a backpack with her. I don't think it's ever been confirmed, aside from her mum telling the friend about a possible compass on the strap of the backpack in Rob's video. Céline intended to go on a short walk, so it would make sense not to bring a backpack. It would mean she carried the glass water bottle some other way however, which in turn might explain why she left it, as it became a burden.
The Butler Road theory doesn't make any sense to me either. It seems so apparant to follow the river upstream, as all the landmarks on the map she was intently studying on her phone just hours earlier are in that direction. I like Rob's theory however, that she used the river only as a guide to locate the water race, since she knew it to run parallel to the river, and that was the landmark she was focused on finding.
