Natalie sacrificed herself for nothing, so what, she followed her feelings no matter how stupid it was. If she didn't live up to your expectations I am sorry, but there are some people like her.
The ending didn't contain everything, she might have ended up going to a nice school after all, who cares if she took a 1-2 year gap.
Natalie is a prime example of an Fi user, which is about doing what feels right, it doesn't necessarily satisfy very logical and rational people's expectations, because it doesn't care.