First off this scene is in ACOS, and she is in no way impressed with it's size, jut notes that it's 8x8 ... there is no evidence of strain, or that she's in anyway holding anywhere near her maximum amount of saidar to use in it's weaving!

aCoS
A Morning of Victory

Weaving a gateway where he had been practicing the sword, a good eight feet by eight, she stepped through onto what seemed to be a ferry, floating in darkness that stretched forever. Skimming required a platform, and though it could be anything you chose to imagine, every sister seemed to have one she preferred.


Even IF your gateway model was in anyway accurate, you don't have enough evidence to actually apply it! We don't even know if Egwene is at her full potential yet, she's further along than Elayne and Aviendha, but that doesn't tell us she's reached her peak. Personally I think she's probably around 90% by TGS, but in the middle of the series she's probably more like 80-85% with Elayne and Avi being closer to 65-75%... but that's pure guess work. Given that most women seem to take as much as a decade to gain their full strength it seems likely that even those Forced still gain the final bits more slowly than the bulk of strength... Moiraine points out that she had the majority of her strength after 6 years of training, but it would be several more before she hit her peak.

Furthermore we know from The Fires of Heaven:
The Far Snows and A Short Spear

"Immediately the gateway began to narrow again, turning, but without thought Rand channeled, blocking it at half its former width." ...

"It seemed narrower than he remembered, too." ...

"Together they leaped into the grayness, Rand releasing the weave that had held the Seanchan in order to fill himself to bursting with saidin..."

So the Gateway Aviendha originally wove was at still about 4 feet across for them to be able to leap through it together ... and since it was less than half it's original size when Rand originally blocked it, it's safe to assume it was near enough 8 feet across to start.

Let's not forget that Aviendha was far below her potential at this time, she'd only been Channeling for a few months when she did this! Speaks loudly that if your theory is correct the women at this level can make far larger Gateways than we've seen thus far.

All we know with any kind of certainty is that Rand can make a 4pace x 4pace and no larger, we have no idea what a maximum saidar Gateway is ... could be smaller, could be larger, could be the same.

And as for Lanfear handling Egwene and Aviendha with contemptuous ease... they never even engaged her directly! She laid a reversed weave on them before they could do a thing! THAT is all about skill, not about strength or dexterity!