What is the ruling on a girl studying from papers that were copied without their owner's permission, knowing that she paid the cost of copying and that this is the only source for her study, and she does not know the owner of the papers?

What the library employee did by photocopying papers without the owner's permission is an aggression and an injustice. It is not permissible for anyone to photocopy or buy these papers because doing so would make them a partner in sin, as intellectual property rights are preserved for their owners. Therefore, your relative is not allowed to benefit from these papers; rather, she must return them and take her money back, while advising the employee and clarifying her mistake. If she needs papers for this subject, she should search for them among her colleagues or in other libraries.