I want to know if a woman who is 60 years old and sick must have sexual relations with her husband? If she refuses is she wrong?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

A wife should obey her husband and should respond to his call whenever he wants to have sex with her if she is able to do so. The Prophet (Sallallahu Alaihi wa Sallam) said: "If I had to order anyone to prostrate to anyone other than Allah I would order the wife to prostrate for her husband. By him in whose Hand Muhammad 's soul is, a wife will never fulfill her Lord's right unless she fulfills her husband's right" [ Ibn Majah ].
Also, the Prophet (Sallallahu Alaihi wa Sallam) said: "If a woman spends her night leaving the bed of her husband the angels will curse her till morning" [Reported by Imams al-Bukhari and Muslim ]. Therefore, she should not refuse his call to have sexual relations without any sound reason. However, she will not be blamed if she refuses his request for any legal reason.
Allah knows best.