I'm not disagreeing that a lot of Aes Sedai are stupid, but this is not an example of it.

Doesine, Yukiri, and Saerin support Egwene. Saerin stood as these two entered the surprise meeting of the Hall (which they were not informed of and which they knew must be anti-Egwene). Since Saerin was standing and they are with Saerin in supporting Egwene, they knew it was something they should stand for. She made that obvious. Egwene had already warned the three of them that there would be a secret meeting of some kind and that Nicola would watch for it.