How do I act regarding my desire to wear the hijab when my mother forbids me, fearing for my academic future, while I am keen not to disobey her since she is ill?

The Sharia has made the hijab an obligation upon the Muslim woman. One should be gentle with the mother and try to convince her kindly about the obligatoriness of the hijab and that there is no room for evasion or compromise concerning it, while being careful not to harm her health.