。
She was on the verge of freezing to death in the snow.
Literal
She [topic-は] snow [possessive-の] inside [in-で] freeze-death just-before was.
凍死 (とうし) means 'death by freezing' — a compound of 凍 (freeze) + 死 (death). 寸前 (すんぜん) means 'just before' or 'on the verge of,' literally 'an inch before.' The combination ~寸前だった describes a near-miss: she came within a hair's breadth of dying. This pattern works with many outcomes: 爆発寸前 ('on the verge of exploding'), 倒産寸前 ('on the brink of bankruptcy').