https://www.paranetonline.com/index.php/topic,21772.0.htmlyeah it's under Other Fae section.
Here's the original source
https://www.paranetonline.com/index.php/topic,36681.0.htmlthe original quote is even longer.
WOJ: "Oh, yeah, so like if the Ladies succeed to kill the Queen, what happens to the Mothers at that point? The thing is that the Mothers are kind of the foundation. So, it’s not so much what happens to them because the little mantles changed. It’s what happens to the little mantles if the big mantles change. So, if someone whacks the being that is, for all intents and purposes, Baba Yaga, and then Mab succeeds, then Mab becomes the new Baba Yaga, and Molly gets drawn up to Mab, and they have to find someone else to become the new Lady. But on the other hand, the Mothers are extremely powerful beings, I mean, they’re really really huge. You can tell because they hardly ever show in the real world. In the Dresden universe, if you don’t show up on the real world, it’s because you’re too big to walk around there. For instance, I think in the third book, when the Dragon is talking about how the Earth couldn’t bear his weight, it’s not that the Earth itself would literally crack, it’s that reality would have issues trying to contain him, because every time he coughs, it would bend around like Neo in the Matrix. So, they spend most of their time NOT on the real world, **unintelligible**, all the really heavyweight guys do that. If you’re in the real world, well, the problem is that you’re in the world, and you’re kind of mortal, and something could come along and try and whack you, if they’re fast enough, or good enough, or lucky enough. Which makes Odin a kind of special guy, because he doesn’t mind it, he thinks it’s awesome. But anyway, you can always tell. If there’s folks who don’t show up in the real world, it’s because they’re super big. So, like, an angel shows up, and it’s just sort of a whispered presence, that’s because he’s just too big to show up here, it’s a giant sandbox, and he’s got to be very very careful to not squash the sandbox. So, he just shows up for that one bit."
I don't know why you're confused about the quote @Conspiracy Theorist?
It's fairly conclusive to me that Mother Winter is Baba Yaga