Originally Posted by Locke.

After her husband died she supposedly went mad and checked into the mental instituiton, that's the reason we get anyway, but my guess would be they planned on making her more important in the long run but decided against it later on.

You will see her again though later on in the show.

I'm reading the encyclopedia later this week which answers some questions they didn't get around to in the show, so it could be in that I guess