“And instead of using force
I guess I should've let you win”

Miley Cyrus – Wrecking Ball Lyrics on LyricsMode
She realizes maybe she shouldn't have forced him to break his barrier. Maybe she should have let him be himself, and sooner or later break away, and she wouldn't be in tragic dispair.
She realised that maybe she should have just left it and let him walk away than creating a war and trying to stop him from leaving her alone.