This isn't really an AIBU but I really wanted a high proportion of responses.
Also namechanged as DP knows my MN nickname.
DP's DM very ill with emphysema. DP and I have only been a couple 3 years, but DM has been ill with this the whole time (not sure whether it had only recently been diagnosed when we got together, but I think she must have had it for a few years before really).
I'm going to use MIL now as it's easier to type.
MIL is still a very heavy smoker and for the past 3 years has been in and out of hospital. When DP and I were first together, MIL used to go out on daytrips and shopping etc. She would usually be up and about the house, and would spend a lot of time outside in the garden. Over this summer she was in hospital a lot more and always seemed to be getting bugs. She also had a minor heart attack (is that the right phrase?) in August time.
Over December she has steadily got worse and worse, she is basically mainly asleep. She is absolutely tiny as she just cannot eat. She is well underweight. Over the past few weeks she has been in hospital more. Yesterday she was taken to hospital as she was vomiting faeces.
DP has always said 'can't wait for my DM to be better'. I'm sure he seems to believe she will get well. She has never talked about the seriousness of the illness, and I think if the doctors had given her a number of months 
that she would not tell DP and her other children.
From my point of view I think these past few days show how bad it is getting, and I think she must be at the end stages.
I don't know what I should be saying to DP when he says 'DM just needs some rest', 'DM will be out of hospital and well again soon', 'she'll be over it soon' etc