It is not permissible to perform Umrah on behalf of the living unless they are not capable. Therefore, if your mother’s illness is permanent (Allah forbids), you can perform Umrah on her behalf though it is not recommended.

And Allah knows best

My mother was about to come for umraah this week ,but last week she suffered with major heart attack n brain attack ,still in hospital in India,can i perform umraah on behalf of her on her name, she already performed hajj n was coming on umraah 1st time ,i stay in jeddah n already performed umraah this ramadaan for myself .