The Creepy Weirwood Ruin Game of Thrones Didn't Show You (The Whispers)

In a feast for crows Brienne of Tarth visits a strange ruined castle called the whispers. Which happens to be the only place we see a "young weirwood" in the books. While here a voice in her head gives her some advice that seems to save her life. This is a chapter where George RR Martin is giving us a lot of hints at various magic throughout his world but doing so in such a way that we are left unsure how much magical shenanigans are actually going on here. Let me know in the comments what you all think about Brienne's trip to the whispers and what might be going on here.