Sabriel

If, after something undead and terrible from another world broke into my boarding school and my 18-year-old prefect subsequently walked up to me, the teacher, and informed me that the undead thing had been a messenger from her father, that her father had most likely been abducted by something else undead and terrible, and that now her plan was to,

1. go off to ski into the Mordor-du-jour-land-of-necromancy-and-the-undead,
2. by herself,
3. to find her father, a powerful necromancer, killed by something more powerful than himself,
4. with only her self-taught knowledge in Necromancy (she had read the entire textbook once!) and her father's sword to guide her,

I doubt my answer as a responsible teacher who had known her since she arrived at the school at the age of five would be,

"Ok, sure, go right ahead, bye!"