。
She fell out of a tree.
Literal
She [topic-は] tree [from-から] fell.
木から落ちた — 落ちる (おちる, 'to fall') takes から for the source of the fall. One of the most basic transitive/intransitive pairs: 落とす (to drop, transitive) / 落ちる (to fall, intransitive).
。
She fell out of a tree.