Don't forget to look at some larger species of beginner snakes such as BCIs(boa constrictor) and carpet pythons, both of which make very interesting and fun beginner snakes. I highly recommend corns and hognoses, but sometimes size matters

My advice is to make sure to talk to the girl about the new pet. Nothing is quite as good as picking out a pet for yourself, and it will get her to do some research before getting her new scaly friend. 17 years old is plenty old to be responsible for a snake(easiest pet to take care of ever), heck I had my first corn snake when I was 8.