We don't know precisely what Nemfection can and cannot do.

My theory is that it does in fact eliminate that limit -- the Lady'sMantle won't even "notice" a Nemfected Lady have sex... become pregnant... even give birth.

It subverts all those things.

I agree we don't know the total extent of Nemesis's power.We can, however, make some guesses. We know that when Aurora was infected, Nemesis did not destroy Aurora's mantle, but rather attempted to take Summer's knight mantle out of play by petrifying Lily. I believe if Nemesis could've destroyed Aurora's mantle, that particular plot wouldn't have been necessary.

My guess is that while Nemesis can infect the holder of a mantle and influence his or her actions, it can not actually directly manipulate the mantle to such a point. If it was within Nemesis's power to allow Aurora to lay with a man and become pregnant, it would've done so, because it would have achieved its goal at that point.

I'm pretty sure Nemfection freed Maeve from all those restrictions, though... She could lie overtly, she could have intercourse with a man, etc.

If Nemesis could subvert her nature to that extent, then it would've been able to destroy the mantle, according to Mab's warning.