Power of attorney is a normal thing, and it doesn't actually indicate that she's unable to care for herself.
It's something all people should seriously consider if they have a responsible adult child.
It has to be done BEFORE you're actually in need, because you have to be competent to make the decision. It saves families a lot of drama if the person winds up in the hospital and someone needs to pay their bills, or needs to make other financial decisions while they're incapacitated.
All that said, feinstein is definitely incapable of caring for herself, so she needs to go. But I wish people would stop demonizing this particular thing, since it has nothing to do with the actual issues.