And yes - you should tell your sister - or at least someone. You should keep in touch with someone at regular intervals so they know you are okay. They should know exactly where you are and where you're going.
I must say I'm astonished at the responses on here. "Great - have fun!" This is not someone going for a walk in the park. This is someone who sounds like they have no experience of living on the land, heading alone into the forest with a backpack and no long-term food supply thinking that being homeless is an "adventure"-- Wake up!
In case you don't read the book I referred to - the subject of the book lasted 113 days in the wild, until he died by illness and starvation. And he was well educated about edible plants and so on. He ended up living mostly on squirrels. Did you think nuts and berries are in abundance? The animals eat them. And anything they can to survive in the brutal wilderness. Plenty of animals die despite instinct and experience. What if you become injured, or sick? Do you have a plan? Do you have a cb radio in case there is no cell service?
If you insist on this, just make sure you are prepared. And that you have a backup plan in place for every eventuality.