As I recall, there are two facets to "stealth channeling." There's inverting a tied off weave- that's when you channel something normally, and then tie it off so it can't be seen/sensed.
Then there's "reversing," which is when you actually channel without being seen.
It's definitely been a while since I've read the books, but I believe that Egwene has learned inverting, but that the the good guys (at least the women) never learned reversing- it's what freaked them out so much about fighting Cyndane in WH. They knew she was channeling saidar, but her shit was just APPEARING without the normal telltale signs of channeling.
“Tolerance is the virtue of the man without convictions.” GK Chesteron
Inde muagdhe Aes Sedai misain ye!
Deus Vult!
*MySmiley*