I am a 7 year breast cancer survivor. I think the thing that helped me the most and what I suggest you do is ask your friend what she needs - would it be possible for you to organize a group of her friends to bring her dinner for an extended period of time? That helped me so much! Books, magazines, etc. were great, too. Also - if she needs groceries, laundry done, house cleaning, etc. The day to day stuff is very helpful because when going through chemo, most people feel so tired all the time.
Please contact Gilda's Club in Dallas. This is a wonderful place for cancer patients as well as a great resource for those who want to help but aren't sure what to do. They will be able to provide you with resources for wig purchases, etc. I hope this helps.