Please check the official website at: https://www.nios.ac.in/student-information-section/question-paper-of-previous-year-examination-academic.aspx for previous question papers in various subjects. If she is a NIOS student, she might be attending study classes but not regular classes. So she might not have the advantage of someone teaching her on a regular basis. So she has to more or less a self learner. She has to make a time table and stick to practising it. There should be no deviations to this. Make her prepare her own notes while preparing each chapter and subject, Lets say for example, if she is reading a particular chapter in Physics, she should make a note of all the important points in that chapter like formulae, theory, laws, etc. Make comparative tables, flash cards, post its, etc. Also ask her to check the previous question papers which have this Chapter's questions and ask her to answer them. This should be the same for Chemistry and Mathematics as well. Ask her to test herself every week by attempting one previous question paper and check her time management and levels of preparation.