Well, you could try a bit of very gentle and very patient Liquifying. But the trouble is, Liquifying softens fine detail a bit. If you'd shot this in such a way (eg very shallow DOF) that the hair was slightly out of focus, I'd have a lot more faith in the Liquify approach. But I reckon you've nailed that hair in pretty good focus, yes? In that case, Liquify presents a big risk of blurring it noticeably.
To be honest, I'd clean up the flyaways nicely, and tell that that's all you can do.
Let's face it, this is a stupid request. You can't be expected to accommodate every stupid request that comes along.