New to the site so I couldn't figure out how to quote, but early in the thread (page 4, third post down by Malaz,) someone asked why Alice didn't see Bella going to meet James. She did see it, and was answered, earlier, she was looking for the "trigger" for that. I think (and I'm reading between the lines here) that when she went to the restroom with Jasper as "guard" Alice must have had some spark of realization of what was happening and the only reason they didn't try to stop her is that they wanted to wait for Carlisle, Emmet & Edward to arrive so they could all go together and stop James. Alice may have had more visions of what exactly to do and where exactly to go while Bella was making her way back to the dance studio. We just don't know it because the story is told from Bella's point of view.
Someone also asked something about why Alice saw Bella as becoming a vampire when a decision hadn't been made. This question was early in the thread too but when I went back to find it, I couldn't, so I don't know who asked. I went to Stephenie Meyer's site and read the Midnight Sun pages that she posted and it explains it well there. Edward hadn't decided yet if he was going to drink her blood or if he was going to keep her safe even from himself. However at that point, he HAD decided that he wasn't going to stay away from her anymore. Alice saw the outcome of THAT decision (giving in to the love he felt for Bella and staying with her instead of resisting) going two ways -- either he'd eat her or she'd become one of them.
Now, on to my question, which is, who was Alice's creator? I read the minute details provided in one tiny paragraph-and-a-half in chapter 22 (I think - I don't have my book handy) called Hide and Seek in Twilight five times and from what I gather she was in an asylum because she had visions (in New Moon we find out that her parents put her there and then said she was dead, putting up a tombstone with her death date the same as the day they dropped her off). From there it gets a little sketchy. What was James doing hanging around the asylum? I gather that there was an old vampire who ran the place (doesn't give a name). I'm imagine it would be a convenient place to work for a vampire if people dropped off their family and planned to never come back and then told everyone they were dead. So was James used to going round to the asylum for some easy prey, or did he see her in town before and follow her there? I wish that Stephenie would have explained it better, because we get a good look into all the other characters' creations in the other books. Back to the point. The old vampire sees that James is on the prowl for Alice and so he changes her, making her safe from James, because he's grown fond of her? Did I get the gist of it?
That kind of says something to me about Alice. If she was charming enough to become the object of an old vampire's affection as a mortal, how much more charming would she be in real life? She deals with the hand life deals her with a positive outlook. "Alice will be Alice." Part of her charm is that she is so confident in what she is doing. She knows what is going to happen and that it will all be good in the end, so she goes on her way, happy with what she has.
The vampires that make up Carlisle's family each play a part in the plot and I don't think that any one of them could be cut. But if I had to pick a favorite (discounting Edward, of course), I think it would be Alice. She can plan my parties anytime.