One possible theme could be survival. If Beth is in the wild, she has to figure out how to stay alive.
Another theme might be self - discovery. Being in the wild alone or in a new situation can make Beth learn more about herself. She may discover her strengths and weaknesses as she faces various challenges. Also, the theme of connection to nature is likely. As she is in the wild, she will interact with nature, and this could lead to a deeper understanding and respect for the natural world.
There could be a theme of adventure. Beth's journey in the wild is probably filled with unknowns and exciting events. It could also involve the theme of resilience. No matter what difficulties she meets, like bad weather or dangerous animals, she has to keep going. And perhaps there is a theme of friendship if she meets other characters during her wild adventure, learning to trust and rely on them.