Hmm - no responses.
Well, I'm not a repair guy, nor do I play one on TV, but here's my two cents anyway. I'ms ure you'll get some pros to respond (once they see what bad advice I'm giving you)
Couple of things - what's the value of the Strat? If it's very old, and therefore valuable, your friend might be better off spending the dough and having a real pro do the work.
If not - e.g. not terribly valuable, then gluing it is certainly an option. What I can't tell from the pic is whether it's a clean break. Doesn't look particularly clean from the back. If I decided to do it myself, I'd first figure out how I was going to clamp it so that the crack was extremely tight, without damaging the headstock further, get some good hot hide glue, and heat the headstock, carefully with a hairdryer or lamp. I'd work the HHG deep into the crack, clamp it, making 100% sure I'd clamped it in line, clean up any squeeze out and leave it overnight. I like HHG - reversible, very strong, etc. One could also use LMI white or Titebond, but I dont like the cleanup as much as HHG.