Clearly Mesaana didn't believe Egwene personally had a "natural advantage in T'A'R" and it doesn't change the fact hat Egwene defeated Mesaana in a 1:1 battle. Circumstances being created (on accident) by Perrin have nothing to do with how the fight between Mesaana and Egwene ultimately went down, or Mesaana's decision to remove Egwene because she realized that Egwene could not be controlled and thus needed to be removed. End of the day, Egwene destroyed two of the Forsaken, something only Rand exceeds while Perrin, Lan, Aviendha and Moiraine can claim one scalp each and none of them have any more "help" from circumstances than Egwene did.
I don't really care how you view Egwene, hate her 'till your hearts content! I'll go on seeing her as an effective enemy to the Dark who accomplished far more than Elayne, Aviendha, Gawyn, Galad, Morgase, Faile, or most other characters throughout the series. No one did anything truly alone, including Rand, but to dismiss what a character did accomplish simply because you don't like them isn't an effective argument. I didn't like Perrin, but he did end up destroying the Shaido threat, unifying a large section of the world, killing Slayer and Cyndane and eliminating the situation at the Black Tower ... All showing how effective he ended up being as an enemy of the Shadow. Me thinking he was a whiner who got thrown into situations where he had no choice but to do what he did doesn't change that he will did these things.