Needs more information to give better advice or we just give a general advice.
For private school, changing course is not a problem as long as you have the money.
For public school like Polytechnic, University & etc, mostly likely you (your niece) needs to quit school before you can reapply for the course you want and that does not come with a guarantee that you can get into the course you want. Your tuition grant will be lesser for next course which mean it can be a problem if you do not have a lot of money.
Most important things are how did you end up in this course and what you don't like to study in this course? What happen if next course is the same thing?
I am checking around on behalf of my niece.