I am afraid that it is going to come to that. You are going to have to look at the Codes of Good Practice on dismissal and in particular, items 10 and 11 of the code. You can find the code here
Basically what this means is that you need to establish whether she can still do the work. If not, will she in future be able to return to work, is it going to be within a reasonable time that she is going to return, is there something else that she can do etc
It does, however, seem clear that she is not likely to return. Remember that you cannot dismiss her for having HIV and TB. Your only criteria must be, is she able to do the work despite the illness. The fact that she did not tell you of the disease is not going to entitle you to dismiss her. The fact that she is unable to do the work, will.
You must get her input in this. So, you need to find out from her as well whether she is going to be able to return to work and maybe set deadlines. From what I hear, however, I think she probably will agree that she would not be able to return.
You are not liable towards her for anything other than her salary that she has worked for, any leave pay that is due to her and any other benefit that she is entitled to in terms of her employment contract. She would be able to claim UIF illness benefits because she can no longer work.
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