Praise be to Allaah.
What the library worker did of copying the notes without the
owner’s permission is a transgression and wrongdoing. It is not permissible
for one who knows the situation to copy or buy these notes; if he does so,
then he is a partner in the transgression and sin. Intellectual property
rights -- such as written works and inventions -- are protected and belong
to the authors; it is not permissible to transgress against them. For more
information, please see the answer to question no.
Based on that, your relative does not have the right to make
use of these notes; rather she should return them to the library and get her
money back. And she should advise the library worker and point out her
mistake to her.
If she needs notes on this subject, she should look for them
among her friends or in other libraries.
And Allah knows best.