I agree OP it really is time for her to go. Mel has been one of the biggest disappointments as a camp mate for me in all the series of IAC. She is causing a very strained atmosphere in there, you can almost feel the tension just watching them when the dinner arrives, and you can plainly see the others are terrified of saying anything, either positive or negative to her for fear of her reaction. And then she refused to take part in a lighthearted conversation about what they thought of each other, like Edwina said it seemed too much of a chore for her to be able to say something positive about the others.
If she is that exhausted and tetchy, she needs to go! It would be a much happier camp without her imo.