I have a friend that wants to make curtains out of this fabric (actually I think she wants ME to make them, but that ain't happening). Is this fabric hard for an inexperienced sew-ER to work with?

taffeta can be slippery, but as long as you pin it well to keep everything in place, it's not bad.

First for her to consider: Taffeta fades and taffeta curtains/drapes must be lined.
Second--good silk taffeta is crisp and has a good hand and must be dry cleaned. Cheap acetate taffeta is limp, soft and used for linings.
Third--taffeta is SLIPPERY and slithery, which puts it out of the beginners' category.

I usually use the term seamstress or seamster, myself.

Taffeta is fairly difficult, yes. It combines slippery with stiffness and translucence, so every mistake in cutting shows like crazy. And any error in sewing the seams shows up as well.

If I were inexperienced, I'd be really tempted to PAY someone to make them (and expect to pay a lot for the pain-in-the-derriere factor).

If that weren't an option, I'd be using wash-out glue (or wash-out glue stick), microserrated shears and lots of patience. I'd use tailor's chalk (the triangular sort from Clover), measure, mark, and then measure again before cutting.

And it frays like crazy to boot! I also agree they would need to be lined ideally with a sun block drapery lining. Lots of work!