My daughter is dying, with maybe a week left. What do I need to? How do I get Power of Attorney?

I'm not even going to get into legal advice right now, but first wanted to say how sorry I am that you are going through this loss.  It sounds truely awful and I encourage you to seek counselors and other professionals through this process. Legally speaking, you can't get power of attorney over someone who is brain dead.  No simpler way to say it.  You also might not be in a great spot in regards to the 9 year old child.  As the grandparent, your claim to this child is likely going to be defeated by any claim of the father.  You will want to speak with a local family law attorney regarding a possible avenue to challenge the father for custody, but again, grandparents don't typically have a lot of rights in this type of situation.