WOW, maybe this is the problem! I am assuming that you have no rent because you are living at home. You have no rent because your mom is subsidizing your existence. Maybe, she is dreaming of the day where she no longer has to do that and you going on a multi month vacation before you are able to support yourself is rather irresponsible IF you are planning to go back home and have your mom subsidize your living. I really get a kick out of entitled kids who think living at home is free. Maybe free for them but not free.
Now, if you are in a position to support yourself post hike then her concerns about responsiblity are not your concern.