Yeah, read books! Birthing from Within is good. I have not read the new Ina May Gaskin book, but that would be good. A slightly more mainstream book is Sheila Kitzinger's Complete Book of Pregnancy and Childbirth. None of the pregnancy and birth books is perfect, they all contain some things that will make you mad. But, they also are good starting points for conversations with your friend.
Ask your friend what she wants from you. You can tell her that you aren't into being doped up for the birth, and ask her if that's what she's planning. She doesn't have to have drugs to give birth in the hospital, and you can help her with that.
One thing that is very helpful is to have someone there to confirm your impressions of how things are going. My dh brought a friend of ours with him to my birth, and she supported both of us really well. She did things like bringing my dh food and me drinks.
Probably the most important thing was that she was with me after my dh took the baby to the nursery. There was a gap when I was actually alone after the birth for a few minutes, which felt so weird and not good because really I didn't want them to take the baby away. My friend came and said, "Is it okay for me to stay with you?" Oh, I so appreciated that!