HiGarry,
I wonder if your sister is on strong pain killers? As they can cause strange things in patients if they are too strong.
It goes without saying she must be suffering from anxiety too, is she on any anti depresants that are interacting badly with her myeloma drugs?
I suggest that you ring her consultant, tell him you wonder if you should be tested for her disease and then go on to ask him to clarify what you can do to help her, and what her treatment plan is.
Get her to buy one of those mini voice recorders to take with her to her consultations and then you all get to hear what has been said and there will be no confusion.
Why not ask for another opinion?
She should have signed a form at the outset of her treatment for all letters sent to her GP in relation to her treatment and how she is responding to treatement ask for copies of those letters to be sent to her, these will help to clarify what is going on.
Try and get someone to go with her in for the consultation, there is a myeloma nurse specialist and sometimes you can get a social worker to attend too.
Her current confusion is good reason to take her to her GP he may be able to shed more light on it. Make sure someone accompanies her as it sounds very much like she needs all the support she can get for the moment.
Speak to a macmillen nurse they are excelent at getting things done.
Hope it gets better and she starts to improve soon.
Min x