As pointed out above when you are in someone else's dream, they are in control. The stronger the personality of the individual, the more control they have. Also, the stronger the emotions involved the harder it is for the dreamwalker to exert control (as shown in the Gawyn dreams, and expicitly stated by the WOs). Because Egwene absolutely HATES Elida, and vice-versa, Egwene would not want to penetrate Elida's dream without great cause. Also, recall from the Gawyn episode how his dreams seemed to almost be chasing her once she found them. I have little doubt that she could have found Elida's dreams, especially when she was a tower captive as she slept in relitiveely close proximity to Elida, but she would not want to. Yes she could find her, pull her into TAR, and turn her into something, but she would have considered that evil. She hated Elida, but did not think her a darklfriend. Now that she *might* be able to justify stripping Elida of the ability to teach the Seanchan traveling, Elida is too far away for her to find.

Also, she discovered the ability to turn Mesana into a child during the crucible of combat, and only after watching Perin ignore balefire by using TAR.

Always remember that there is a difference between what you can do, and what you should.