To be entirely fair, I am like 90% certain that when Yang says 'you don't mean that', it is NOT meant to mean 'you don't mean the fact that you are being negative and upset and angry shut up and go back to the positive person you are'. Its Yang sliding into mum mode and going 'you don't mean to be that hurtful and antagonistic.' Yang isn't denying that Ruby is upset, she's saying that Ruby isn't planning on being hurtful.
It's like how Jaune snapped at Ruby in his anger and pain and was able to realise his error and apologize to Ruby. Jaune didn't mean what he said, it was his tramua and negativity speaking. It still hurts though, which is why he apologized for it. Even if Ruby wasn't in a place to listen or accept it at the moment. Yang knows Ruby, Yang basically raised her as a kid. Yang knows that Ruby doesn't truly mean the harsh, hurtful words she's currently saying. That's why she says she doesn't mean it, because Ruby doesn't.
At least, that's how I'm taking the scene, inspired by the metas of others on the exact same subject.
yang's "you don't mean that" is from the previous episode when they're talking about salem and the relics and saving people in atlas; ruby is frustrated bc what does it matter if they saved everyone in atlas (which, ya know, i think the people cinder blew up off the bridge beg to differ) when salem is closer to getting all the relics and will destroy the world once she gets them all, and she airs that frustration out only to be met with "that's what ironwood thought. you don't mean that."
and like. that's a valid concern to have; ruby doesn't think that saving people doesn't matter but if they keep losing the relics to salem while doing so, which they believe will end in the destruction of the world, what's the point? they're just running in circles, not going anywhere. the people they just saved will die in few months anyway if they can't find a way to stop salem or get the relics back. why can't ruby say things and actually mean them, to think their current methods aren't working and it's all pointless, but yang gets to not only think but to say it out loud that ruby's amity plan couldn't be done and that it was pointless bc there was no guarantee anyone would come to help?
more importantly, why does yang get to decide what ruby actually means? jaune lashed out and apologized on his own. ruby didn't. maybe she did mean every word she said while lashing out. maybe she didn't. point is ruby is the only one who gets to say what she meant and didn't mean. not yang.
and like. nothing is worse than finally getting your words out—even if it happens in an ugly manner like it did with ruby—only to have people minimize it and invalidate what you just said bc they "know" you better than you know yourself. all you can think is that if they really knew you, they would have noticed much, much earlier that something was wrong.
