Personally, I thought it had something to do with not harming the babies. - Edit 1
Before modification by Shannow at 09/12/2010 10:01:27 PM
Using it's full power would most likely put her at around Lanfear's level.
Ignoring the implication here that a woman who is likely around Cyndane's strength (I mean Nynaeve) is only 75% as strong as Lanfear...
Why would Elayne be worried about seeming as strong as Lanfear? The stronger she seems, the more intimidating she'll be! The only reason for her to restrict herself is to not go too far.
And I notice that you have no explanation for why Elayne drew the full amount from the angreal only a few paragraphs later. What, the angreal increased in strength?
But nevertheless, the angreal is not needed to prove the strength differnce between Elayne and the weakest female Forsaken.
Egwene has already demonstrated that for us.