Is the hijab an obligatory duty upon a mature girl, and is she sinful for not wearing it since she reached puberty?

The hijab is an obligation upon a mature girl, and it is not permissible for her to appear before non-mahram men without a hijab. She should not be deterred from this obligation by the widespread immodesty in society. It is obligatory to hasten to wear the hijab immediately. As for the month that passed without hijab after puberty, it is a sin that requires repentance, and repentance erases what came before it.