It's a lovely thing to do for your friend.
I have been thinking about what I would like if it were me... I would want to know there were people there for my children, forever, not just for the immediate period. So reassurance from everyone re that. Same for DH. I would find great comfort from seeing things like a photo album of my friends with my children with just a couple of photos in it, with promises that they would fill them up when I'm gone. Knowing my friends will talk to them about me. Will make sure they know how much I loved them and didn't choose this...
That would mean the world to me.
Spending time with me.
Other little things... silly nonsense 'Shopaholic' type DVD's/books, Kendoku (like sudoku but harder), good for occupying the brain (if she is still up to it), lipgloss, hand cream (Clarins is nice, not too strongly scented or greasy), new PJ's etc.
As someone else said, if she's at home, clean & ironed sheets changed often.
If she is able - any food, drink, sweets she likes...
I am sure, that no matter what you put in, she will love how much thought and effort you have put into it...
x