I don't know what the law in switzerland is like, but in britain it would quite hard to qualify her either as being a danger to herself or others, or demonstrating that she is incapable of looking after herself. Saying that it wouldn't stop some do gooder in authority trying to do what they think is best for her. I really hope that doesn't happen.
Wolverhampton had a old bloke that lived on the central reservation of the ring road for many years. The Sikh temple looked after him as they would any Indian sadhu as he demonstrated a life without an attachment to material needs. From John the baptist, to Buddhas in disguise there is something in this woman's life of nomadic hermitage that would be perfectly acceptable in a community with a spiritual dimension. It would be the greatest shame if modern Europe can't find an acceptable space for the batty woman who lives in the woods.
Crikey when i get to forty i might join her road 12 years, I certainly have days when running away and living in the woods on my own seems a perfectly sane option.