Meg, I'm so sorry about the loss of your friend. My sister's best friend died of cancer 2 years ago and she was like a sister to me.
I flew down to be with my sister the day of her friends passing and I didn't leave her side for a week. Like Nelle said, make sure she is eating and drinking, and getting plenty of rest. You're already being a fantastic friend by offering an ear for her to talk to, and just physically being there for her.
The time of the funeral, she, and you, may feel numb about it all. But it's afterwards that will be just as important as now. That's when I think the reality kicks in. If you feel she isn't coping, encourage counselling. It's the best way. Unfortunately as I was living away from my sister at the time, I couldn't be there for her as much as I wanted, and she didn't seek counselling straight away. She went into depression. She is now seeking help for that.
for you. This is a difficult time. And remember it's best to let it all out, don't bottle your feelings up.