Just a Memory
It's hard to say exactly how much we know about Mal. At first we're tempted to picture her as an evil, vindictive betrayer who is trying to ruin her husband's plans. While this is certainly true, we have to keep in mind that this is just a projection of Mal—not the real Mal.
We actually never see the real Mal except in flashbacks, and all of these flashbacks are of her post-inception self, when she is in a sort of confused state, unsure of what is real and what is not. Really, the only info we get comes from Arthur who, when asked by Ariadne, says, "She was lovely."
That's nice and all (thanks, Arthur) but maybe the movie is more about the evil projection Mal than the "real" Mal… since we never even meet the "real" one at all. In some ways, projection Mal epitomizes the femme fatal: an archetypal woman who lures men into dangerous ground with her womanly charms. (It's a moldy-oldie archetype that has been appearing in western literature almost since its genesis, but it has become particularly popular in film with the development of the film noir. Think Lana Turner. Think Barbara Stanwyck.)
Where this gets weird is that we have to remind ourselves that the Mal we know is a part of Cobb. When Cobb says that Mal has Fischer in Limbo because she's trying to draw him there, it's really Cobb himself that subconsciously wants to return to Limbo to be with—or essentially pretend to be with—Mal.
Needless to say, Cobb is a messed up dude. Most people don't subconsciously stab themselves in the chest.