If the Queen did have myeloma, she must have been in tremendous pain at times. And most of her family must have known about her illness (I don't think the Harkles knew. I think it was kept from them in order to avoid their exploiting it for financial gain) and that her time on Earth was coming to an end.

I can imagine there was jealousy between HM's Ladies and Angela Kelly. However, no one can deny that Kelly served the Queen very well and was a trustworthy close friend of the monarch. I have no doubt Kelly will take many, many confidences to her grave.