Power steering fluid.

my mom was driving today and as she was turning the steering wheel didnt wanna turn back. My mom thought that it was the power steering fluid and we went and bought some but when we went to put some in it was full> what could be wrong?

if it did not want to turn back there could be some parts binding under the vehicle. the only thing that makes the tires return to a strait position is the alignment of the wheels, so maybe that has been bumped out somehow. if you cannot see any parts touching or seems to be moving with a lot of resistance, take it to a qualified mechanic with a alignment machine and have them look at it.