Didn't carefully read PP so forgive if repetitive :)
I think my OB would've wanted to deliver me no later than 37 weeks with my twins. (sadly, I only made it to 32.5, and had an emergency c-section due to HELLP syndrome; luckily both babies were totally healthy and did not require resp support after birth!)
In my case, the presenting twin was breech at 32 weeks. Baby might've turned by 37 ... we'll never know ... but my OB said I could try for vaginal birth if presenting twin was head down. I have two prior successful vaginal births, so I think there was no reason to believe I would be unable to deliver smallish babies vaginally.
I can't remember what the "rule" was on epidurals, but knowing that this particular OB/hospital is epidural-happy (one of my very good friends was going to her for a VBAC but switched to a midwife practice after being repeatedly, constantly barraged about not having an epidural ... it just got too discouraging!) I probably would've been required to have epidural in place and deliver in the OR if I had gotten that far.
I think that it is totally possible to deliver twins vaginally (esp if not first delivery, and not a vbac trial; though I had a close friend who had identicals as her 3 and 4 and intended to VBAC with the twins in a hospital, w/ epidural in place; unfortunately her water broke but no labor, so she ended up with a second section for her twins). However, your friend just needs to look at the ultimate tradeoff -- best case is vaginal/no drugs; worst is c-section/general anesthesia (b/c epidural not in place, so in a crash setting, it's all the way under for mom -- which has risks to her and to the babies).
Last, I saw one PP message referring to how hard it is to nurse twins, especially preemies, even when an experienced nurser ... I wanted to second that BIG TIME! I had 2 prior kids, nursed them both exclusively for 12+ months, no issues at all. With the twins, we brought them home @ 36 weeks gest. age, weighing under 5 lbs each (what was the NICU thinking?! LOL) One twin took to nursing pretty well/effectively/quickly; the other, it was all the way until due date that he started to get the hang of it. It was a brutal 4 weeks ... lots of tears (on my part), second-guessing myself, LCs in the house, weigh-ins, etc. But in the end, WE PREVAILED! And the twins were EBF until about 14.5 months. So it all ended well ... but it was HARD. I agree with PP that I would not agree to an induction at 36 *if* everything looks OK for the babies. I would agree to 2x a week U/S or monitoring to be sure they're OK ... stuff can go downhill really, really quickly at the end of a twin pregnancy, so you do need to be reasonable/cautious, but if things look good, then no reason not to go until labor starts itself, but NOT PAST 40 WEEKS, period! (IMHO ... I am not a doctor!!)
If she really wants a no-drugs vaginal birth for twins, and both twins are head-down, and everything looks totally normal on monitors and u/s, she could wait for water to break/labor to start, and then stall a little on going to the hospital ... not too long, but a little delay ... to increase the odds that she will be given the "mandatory" epidural ??? Remember, I'm not a doctor ... but my thinking is this -- if she gets to the hospital at 7 cm, she has a better chance of avoiding pitocin/epidural than if she gets there at 0-1 cm (or is induced from a zero). But again, this would TOTALLY be dependent on everything being totally perfect at every prior exam/ultrasound/monitoring, etc. And it would not be without risk. It's all a balancing act between her perception of risks and benefits of all the options.
So, just something to ponder. Undoubtedly someone will get on my case for suggesting a small delay, but that's how it goes!
Sorry I went on so long :)