Alee Ibn Taalib (ra) related that he heard the prophet (saw) once say that if a man calls on his sick muslim brother(or sister), its as if he walks reaping the fruits of paradise until he sits and when he sits he is showered in mercy and if this this was in the morning, 70 000 angels send prayers upon him until the evening, and if this was in the evening, 70 000 angels send prayers upon him until the morning.

subhanallah i just wanted to share that and remind us (including myself) of the excellence of visting the sick.

I pray your sister in law gets better inshallah. There is a du'a that you can read when you visit her. The prophet (saw) use to say. La-ba-sa tuhur insha allah. (never mind, may it(the sickness) be a purification if allah wills.