An important question that nobody here seems to have asked is this: How heavy is your friend, and what kind of terrain will she be riding on? You've already mentioned that this is for a single-speed freewheel build, she's not a commuter, and you don't expect her to put thousands of miles on this or any other bike, so I'm guessing we're talking about pavement only, no curb-hopping, and nothing crazy. If she's pretty light, I'll beg to differ with just about everybody else on this thread and say that you're completely safe going bottom-of-the-barrel on the cheapest regular cup-and-cone hubs you can find.

The reason I say this is because I'm a 160 lb daily commuter in wet, nasty Boston, and I've put 20,000 (yes, twenty thousand) miles on a low-end Shimano Acera freehub that I've had on my Kona for 11 years (almost worn through the rims on the front wheel of that one), which sees mostly commuting with some curb-hopping and some light mountain biking, and around 10,000 more over 5 years on a bottom-of-the-line Quando freehub and 4 years on a Quando track hub which see only road riding. All of these are basic, not-really-sealed cup-and-cone loose-bearing hubs, but I keep them well-adjusted. My tandem has higher-end hubs.

To be fair, I've never broken a spoke either, but I keep those tensioned pretty well and I suppose I've been lucky. But I really suspect that for your friend, unless she's heavy, even mid-range components would be overkill.