Fitst I will suggest you to join any coaching classes.Because as she is preapearing for IIT JEE then she will face a tough comptition. coaching classes can guide in a better way.
from 11th standard is the best time to start prepration for IIT JEE.beause now IIT JEE has limited number of attempt ,one can attemp only two time one with 12th and one just after the 12th.
and regarding the self study.certainly she can do self study.but if she will do self study then she will miss lot of concept which is not well explained in the books or study material .and it will affect on your final result.
you can take BRILLIANT material,or fiit jee material ,or ASKIITian study material.
ASKIITIAns.com also provide series of interactive Recorded lecture of physics chemistry and maths.which is very helpful in jee prepration.
click here for more details about the packages in Askiitians .com :
and there are also some good books for jee prepration.
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