Sorry for the lack of posting this week. While I'd like to hide under the busy schedule excuse, the truth is that I had more... *ahem*... Potter-esque activities to complete. And, might I say, it was utterly fantastic. :)
But back to the question at hand: Just who is Libby and what's her agenda?
She has two significant connections to two of the Losties, Hurley and Desmond, but we know so little about her it's really hard to say whether her associations with them are simply pure chance or something more sinister. And, believe it or not, I'm actually thinking it's the former. Bear with me here...
We know that sometime before 2000, Libby lost her husband and, shortly after that, she ran into Desmond in a coffee shop and gave him her husband's boat. Remember that Desmond crashed on the island in 2001 (three years before the plane crash) and that he took a year to train. Now this meeting could be simple chance - her emotion and offer to me seemed genuine. She was obviously pretty upset over his death and it doesn't seem that strange that she gave it to him.
Could Charles Widmore have put her up to it? Sure. But chance just seems much more plausible here.
But what about her association with Hurley? It could be that she never got over her husband's death and that sent her to the mental institution. This fits with the timeline (i.e. she ended up there after she gave the boat to Desmond) since Hurley was in Santa Rosa right up until shortly before he won the lottery.
Now it is possible she was stalking Hurley - she must have gotten out of Santa Rosa shortly after him, probably saw that he won the lottery, and followed him to Australia. Remember, we still have no idea why Libby was there in the first place. But maybe she really did take notice of him in the institute and formed some sort of obsession. And if she was stalking him, it kinda explains her attraction to him and why they were both on Flight 815.
So is she really a psychiatrist, or did she lie because it's better than saying that you're a mental patient? Assuming there's no malevolence involved, I'm thinking the latter.
The only argument against all this is that it's pretty amazing she ended up on the same island with Desmond. Could she be a spy for someone, maybe another one of Ms. Hawking's pawns, working towards making sure both Desmond and Hurley ended up on the island together? Was it coincidence or was it fate? What do y'all think?