Ed,

That's the shadowing of her lips on the teeth. Try a very soft light shining directly into her face.

So far as seams, I haven't seen any issues in the renders I've done. Occasionally, depending on the software and etc, you can get seam-looking things in Preview, but 99.9999% of the time, those rectify themselves when passed through Firefly/3Delight.

On render times and lighting: Blackhearted sent out a beautiful tutorial with GND4, that I absolutely recommend to anyone. The tutorial alone is worth the price of admission.

I'm going to get off my soapbox now, and let you get back to your day