One significant difficulty in answering this question is that we don't know exactly what the conflict is. The husband tells Mary that he will give her money "and see that [she's] looked after," which implies that he's leaving her, perhaps for another woman. Mary's way of dealing with this conflict is, of course, to strike her husband over the head with a frozen leg of lamb, killing him on the spot.

Whatever the exact nature or cause of the conflict might have been, it's possible to imagine lots of better ways in which Mary might have resolved it. The most obvious alternative route to resolution would have been discussion. The marriage, at least from the husband's perspective, has clearly lost lots of the love and affection we can presume was once there. If Mary had spotted her husband's unhappiness earlier and spoken to him about it, perhaps they might have found a way to resolve it together, before it grew into the hostility we can infer at the beginning of the story.