Need Some Info Please

My Aunt just found our one month ago she has stage iv lung cancer.It is in her hip and many brain tumors..they cant do surg.She is almost done with her 3 weeks of radation.and goes weekly for 6 months for chemo.the dr keeps telling she need a power of attorney..So that is me.she doesnt want to talk about it and doesnt want to know anything.I want to know some family members also have seen her start to get a little forgetfull and very mean but thats her anyways.the dr said he isnt worried about the lung now its the brain tumors.My question is what next.I am worried sick she will not talk about it.We get the papers signed on monday and I want to ask the dr lots of questions.Am I wrong she doesnt want to know but I do also does other family members as we have to care for her.she is 66 and its very hard to see her weak cant eat and just mean and getting worse.she always has been spitefull but it is to the point now it it her normal state or is it the brain tumors.why do the drs want a power of attorney so bad? Also she will not fill out a living will...I dont know how long she will live but i want to make sure she is comfy she has no pain.I worry about her living alone and doesnt want anyone to  feel sorry for her.any help would be great or info anything.I can take the truth thank you.TOday she has her last radation treatment..She now is so honery with everyone and so what signs do we need to watch for.She doesnt sleep and just lays around and doesnt want to talk to anyone.She lives alone.We cant get her to do anything.The dr ask her if she is depressed she says no I am not.And she is.they ask her if she sleeps well she says yes and she doesnt.please any help would be great thank you. 

Your mother is having a hard time...remember she is very sick, and probably depressed...it hurts the patient to see how her illness affects the ones she loves. She doesn't want people to hurt so she is pushing you away, give her some space, it is not her fault that she is ill. And she needs to know that, be there but try not to get in her face too much, she has a lot to think about and her paper work should be in order, i am in remission but i got it in order just because if she needs you to write a check or pay her bills you will not be able to do anything. She may need help later on.  I went thru alot and i did not want my loved ones to hurt...you say she can be mean spirited but that is a good cover up for her feelings, she wonders why me and what is going to happen, god loves her and he is there,give it all to him. God bless you all