I had my first mortgage when i was 18. I wouldnt worry - it will probably teach her so much about the ways of the world.
As long as she proved that she has the 35% earnings to debt ratio, she would have gotten the loan no prob. banks are so lame with stuff like that, they give out loans to anyone basically, even if they have only been employed for 2 months!

But seriously, i think this will teach her some responsibilities. And if she screws up, its a great lesson in life!