My sister is drifting away from Islamic values

Assalamu alaykum, My older sister has started saying some things that really worry me. She used to claim that hijab is just a man-made rule and not from Islam-that it's something from Arab culture that brainwashed us. Now she's gone further and says mahrams don't exist, that they're just a way for men to control women, and she tells me I've been brainwashed too, saying "you'll see on the Day of Judgment." I know deep in my heart that hijab and mahram are part of our deen. I have no doubt about that. But what I'm struggling with is: does saying these things take her out of Islam? She's basically saying something haram (not wearing hijab) is halal, and the same with mahrams. The mahram issue came up because I wanted to go for Umrah with my mahram, and she called it brainwashing. When I pointed out that it's in the Quran, she just said she's not debating. Honestly, I think she avoids debating because she knows she's in the wrong. JazakAllah khair for any advice.