Can my divorced sister visit her ex husband in hospital?

Asalamu alaikum, my divorced sister who has 2 adult sons with her ex husband. She wants to visit him in ICU. She left her home because of mental health as he denied that his divorce counted. Also she worked and paid towards and maintained the home that they shared. He did not give her anything of that property and didn’t pay towards the children neither. Is she allowed to visit him? Could you advise please