At one point during the fetus boss battle Lilith says a curious thing.
"For god's sake, hit him back!"
Basically she's telling Munbaby to fight harder. Now the expression "for god's sake" is used to convey frustration, desperation, anger, surprise, all that jazz, and Lilith has good reason to feel this way because by this point in the battle she's losing.
But she's a demon. Why would she be invoking God's name? Can you imagine an angel saying, "For Satan's sake"? It's odd, isn't it?
It's an oversight in the script that's for sure, be it intentional or not, but since it's there let's come up with reasons why she's able to say that and not be struck dead by the Almighty Himself, or at the very least have an angel swoop down and cuff her upside the head.
I'll throw in my .02 and say that God and his angelic army have little to no influence in the human world, and that demonkind is not as allergic to holy names/symbols as they probably should be.