Round 1: Even taking into account the relative equality that being so strong in the Power gives the Forsaken in a fight to the death, Lanfear is very mentally unbalanced, and I think she'd be willing to pull out powers and skills that would not be easily defended against. If Graendal got the drop on Lanfear, though, she'd win - she beat Cyndane and Moghedien when taken by surprise herself, so I think the Forsaken females are more powerful in sheer capability than the males. At that level of power, heck even at Moghediens' level, what really matters is who sees who first without the other watching; none of the remaining Chosen were arrogant in their strength enough to leave their backs unguarded while The Spider was in the game and I think it comes down to being equally dead regardless of what magnitude the fireball/brain blasting/lightning bolt/pain inducing/flash freeze creating weave was.

Round 2: both are shielded, total catfight: Lanfear is crazy enough to skin Graendal with her bare hands, whereas Graendal likes to give orders and watch others carry them out.