On the suicidal stripper theory and coming back from the dead:
I'm taking the easy way out on this one, but it could be all considered a matter of perspective. Remember the holes James jumps through? Who's too say the fall wouldn't kill him (And I still like reffering to that Silent Hill ending. Hell would truly be not realising that you're dead already. Think about how big a mind-fuck it would be to wake up one day, faced by indescribable monstrosities when in fact you died the night before)? Essentially, the town is one huge mind fuck. We never actually see Maria getting stabbed by Pyramid Head's spear during the hospital chase scene (Remember, you get game over if she does die during the chase). As far as I recall, the only moment where you actually witness her death is near the end, with the two Pyramid Heads.
Finally, I don't think the demon in sheep's clothing theory works. In one ending, you actually face off Mary, not Maria. And we already established that Maria dies by the hand of the two Pyramid Heads.
Just my opinion, but I think that considering Maria as a normal person, not a monster, but who's being controlled and manipulated by the town to make James suffer is far more entertaining and amusing. Kind of adds to the humanity of it all. It's very possible that Maria loses it, hence the dialogue in the labyrinth, thanks to the towns influence (Remember, there too, you don't witness her die. You only find the body later). If anything, one thing that has to be known due to the way how monsters are perceived differently from person to person is that nothing should be taken at face value.