We brought my MIL to live with us a little over a year ago. She has a lot of little aches and pains that the doctors are attributing to old age. She has started groaning and moaning more each day and often talks about dying and she will not be here much longer. Any suggestions on how to talk to her about this?
I'd take advantage of her preoccupation with dying to get some planning done. "Mom, we are all dying. That is the natural course of life ... we get closer to our death every day. At your age you are probably closer than I am. Let's talk about your funeral or memorial service." Find out what her preferences are. Does she have a will? Are her affairs in order?
and ... "Mom, I hope we have you with us for years yet. Is there anything you've always wanted to see or do, that we could do now, before it is too late? Would you like to visit your sister? Haven't you always talked about seeing Mount Rushmore?" (Only suggest things that are possible, of course.) Talking about living before she dies might be more pleasant for both of you. Focus on "What do you want to do in the time you have left?"
Don't argue about whether she is or isn't dying. Respect her perception. Just move it in a useful direction.