Here's my theory.
Michael made a trade with the others. If Michael brought "Henry Gail" back, Michael would get Walt back. He said sorry to Ana-Lucia because she was the only person in his way.
He accidentally shot Libby.
And when he "shot" himself, he seemed to have done it at an angle where it would have been at his arm only. So he can make it look like as if "Henry Gail" got in control of the situation.
The compromise is when Henry Gail returns to their camp, Walt is set free to come back.
Of course, Locke just told Jack of what's going on and they're headed to the hatch as "Henry Gail" makes his way up.
Dun dun dun.
Edit: Ehhh...the drunk driving thing. Irrelevant? Her incident occured a week or so ago. And I'm under the impression they've had this episode ready for quite sometime. Maybe even a month or so? That or I'm really ignorant about the TV world. So maybe she thought to herself, "Hell! I've got nothing better to do!"
Plus I doubt they would cast her off because of that. Didn't the same thing happen to Eva Langoria(sp)?