If she's in the East, and going west, that should make the trees thin out. This seems to indicate she's going the wrong direction.
But she can measure the sun in the sky as if it was her own body - she's going west, she's checked. So. She's not in the East, or something else weird is happening.
This definitely seems like the Pole of Wood. All the descriptions she's heard match it. It's definitely not the ocean, anyway. And this isn't the Blessed Isle, desert, coasts, or ice. That limits the possibilities. Which leaves The Underworld, Hell, Heaven, The Wyld, or something even weirder.
It's not Hell or the The Wyld. The Sun's here. It might be the underworld, she doesn't actually know how that works, but her essence is regenerating as normal, and this place feels very alive. It could technically be Heaven, but she doesn't remember know of any rainforests there.
...She'll split the difference and go north. Staying here isn't going to be useful, and the treetops aren't nearly as inhospitable.