Hmm, Emily is not really a character I enjoy too much.
Perhaps it has to do with my dislike of imprinting but whenever I read of her and Sam, I read it as a tragedy. It is a sad story and since I don't believe imprinting is about love, it's not one I can find any happiness in.
As for Emily's character, I read her as one of two things and it's something I have never made my mind up on. To me she is either selfish or weak and neither of those attributes make her an endearing character in my eyes.
To sacrifice someone who was once as close as a sister for a man you've just met is unforgivable. Though I agree with those who say that imprinting is almost as hard for the imprintee than the imprinter to resist, I also find it hard to warm to a character who could give up on that fight.
I know Meyer has talked of a scene in which Emily tells Sam to go away out of guilt for Leah yet then we hear that she has asked her to be a bridesmaid at her wedding
From what we know of Emily's character, she doesn't appear to be malicious, so I'm willing to accept that as a momentary lapse of judgement on her part.
I think that of all the characters, Emily is the one I like least. With Rosalie and Leah, I can accept their coldness and cruelness because even without knowing, it was easy to see or imagine the motivation behind them. With Emily, I can see only motivations that benefit her and that is why I never seem to be able to sympathise with her character.
I don't think finding out more about her would ever change that because I am one of those who believe there was no excuse for what she did, though I am not adverse to adding more of her in the movie if it fits.