That was the only thing that grated on me, as well.

But the other stuff? How else would she react?

Her losing her composure highlights Moridin's unnaturalness and his potential transformation. Besides, she's messed up big time so why should she be calm inside?

This effect is also majorly repeated in her last scene where she is packing up like a junkie. Yeah, it was funny to read, but it makes sense.

Unless of course you're one of those readers who erroneously put the Forsaken on a pedestal. Tip: They're painful human.