My twins are 3 years old now, and I fed them until 2yrs 6mo an 2yrs 9mo, when they each decided to stop.
I always fed them one at a time, whenever they each needed feeding. I didn't ever master feeding them at the same time.
I also didn't get on with feeding cushions (tried widgey cushions and EZ to Nurse.
Once they got to 4 months, I mastered feeding lying down. This saved my back a bit as I spent less time sat up in bed feeding.
I coslept once I could feed lying down. Complete sanity aver as I didn't have to get out if bed at night :)
Prepare to feed, feed, feed and feed in the first 8 to 10 weeks. If you feed them separately then it is relentless as you pretty much take one off and put the next on. It used to take me 2 hours to change, feed and settle both babies, starting every 2.5 hours. So I lived my life (toilet, making food, showering) in half hour blocks!
It is really hard work in the first two or three months. The pay off is amazing though - I travelled the country on maternity leave, biding friends, staying with people, going in days out. I didn't have to worry about taking anything with me - a spare set of babygrows, a pack of nappies and wipes in the car and I could be away for 2 hours or 2 days! Never had to worry about getting delayed as I was all they needed to survive :)
I agree with the previous poster who recommended Tamba and their leaflets. You can send off for them from the Tamba website (and it's worth joining for their magazine).
Good luck to your friend! Don't let anyone tell her it's too hard or she doesn't have enough milk - if she keeps feeding then she will make enough milk, and many people have successfully fed multiples :)