Hmm...that is kind of a hard question. I don't know what she will be, although it sounded to me like she had turned evil. If she did turn evil, though, she would be very hard to defeat because she could sense every move you tried. Remember when Eragon was about to hurt her, she stopped him. (I think he was going to kill her after he had cast his spell, but I don't remember that well. Does anybody know if I'm right?)

Well, as far as I remember Eragon was not going to kill her, he just wanted to continue the spell, meaning that since the first one did not worked, he wanted to stop her from feeling all the soffering!
Nevertheless, I think that if Elva joins Galby....its going to be a #@§%£#@!! But she likes Saphira and she is thankfull to her, which is a good thing