Been a while since I read the books but I'd say
Couple of reasons. During her annoying dull to read (from a guys point of view) depression in new moon she starts going all adreniline junky which show a very unhealthy Se. Also her thought prossess is quite Ni-Ti orientated. For someone very emotional she is very logical at times. She is also clearly ver intuitive in her logic. Its far more make the connection then think it through briefly thus Ni-Ti. Fe is clearly secondary as she has a good understanding of the relationships between her girlfriends and all their boyfriends. But is detatched enough from it to be irritated by it all at times.
Edward - hmm tough definatly IxxJ. best guess is INTJ
Probably easier if I read book 5 on the website but I've only got internet in work so not possible the now.
Right don't think its despute able that edwards I. T makes sense as while yes you see lots of his emotions you have to remember you see that in a romantic book from the point of view of someone completely fallen for him therefore its biased. But some of the things he does are very logical. logical but clouded by an undeveloped emotional side. He also very practical in his logis and personal in his emotions thus TeFi. J is from his decisiveness in his decisions. He is able to make decisions and stick to them. Its far from impossible that hes P but i think its unlikely. finally N. This is what I'm unsure of because the difference between Si and Ni is very difficult to tell especially with a character with such hidden thoughts. But Ni wins out. Mainly because he seems very detatched from the world to me. For someone so able to see and experience it he seems so cynical and withdrawn. Also he is so extremely intelligent (not that ISTJ aren't) and so arrogant at times that INTJ makes more sense to me.