(a) when she is recovering from malaria.
(b) when she has recovered from malaria and is taking care of someone suffering from chicken-pox.
(c) when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox. Why?
In condition (c) she is more likely to fall sick as she has just recovered from malaria but her immune system is still weak and she is not taking proper diet. At this stage her body will not be able to fight against infection and if she is taking care of someone else suffering from chicken pox even she can get infected with chickenpox virus and will fall sick again.