Siuan knew her ability with Healing had not changed after being stilled and Healed.

Elayne already knew that she could only Heal bruises before we see her Heal Rand in TSR. Must have tested it out somewhere along the road.

I wonder, Egwene clearly knows all the various Healing weaves (new and old), seems to me that she would have had to have used them in the camp at some point while learning. How else do these women all know precisely how much Talent they possess...

Healing seems to me to be one of the OP mysteries out there... in EoTW Moiraine Heals Tam, but he's still bed ridden for days afterward, Mat is similar, but his wounds were different than a slash from a Fade's sword.

Early in the series Nyn/Eg/El talk about how Healing is considered too dangerous for Novices/Accepted to be taught. yet by KOD Tiana is letting them learn the new weaves as well as the old. Perhaps the Tower has just began forcing Novices in anticipation of the LB? Of course with all the older women entering the Novitiate it's possible that they are just more mature and learn at a much faster pace than young girls.