Just the falling kid is enough to make this at least a plausible theory, and he doesn't have to still be ta'veren by the time he meets Suian.

This conversation is fun. But...

Lanfear disguised herself as Else and lead the girls to the "subtle" hints to Tear. As she was giving them the directions, she stared at the ring.

The first words out of "Sylvie's" mouth are: "Well, you've found your way at last".  Clearly showing she had been waiting for Egwene.

She also knows that Ishmael is Baalzamon, and uses similar phrases talking to Egwene as she did talking with Matt.

And if all that isn't enough, the Compendium states it outright.