I can understand Justin putting Elaine under his thrall with the eventual intention of getting to Harry as well but he had Elaine hold Harry down magically so he could get inside Harry's head. If Justin was able to take down Elaine without any help, why did he need her to help him with Harry?

Justin should have been able to do whatever he did to Elaine to Harry. So either Harry had more natural strength and abilities than Elaine and I don't think that's been suggested. Or Elaine wanted to help Justin. She was young, he was very powerful and she no doubt had a great deal of respect for him.

My personal feeling is that Elaine was trying to impress Justin and didn't think that Harry would get hurt so she went along with it. Of course I could be wrong. ;-)

--Elizabeth