What is the reason for the student's declining academic performance, her hatred of studying, her inability to concentrate and remember, and her repeated failure in exams, and what should she do about her feelings of despair and shame towards her family?

It is recommended to continue supplicating with certainty of a response, and to be patient because patience is the key to all good. Also, frequently remember Allah Almighty, strive to associate with righteous women, and exert effort in identifying the causes that affected your academic performance and addressing them. If no ordinary cause is apparent, there might be magic or an evil eye, so you should perform ruqyah (Islamic exorcism/healing).