That was her statement, in a context strongly indicating she meant "once EVER," not "once in that session."
To be fair, she could have and quite possibly did spend more than one day TRYING to channel, but she only spent one MOMENT actually DOING it. The Tower undoubtedly trained her in myriad OTHER ways and continually primed her (or tried) as a potential lever on the future queen of the powerful neighboring nation that was the largest known. That does not, however, mean they wasted any more time training her in the OP once she finally managed to satisfy their technical need to see her use it for a brief instant. It actually argues just the opposite: The Tower had FAR more constructive ways to use its access to Morgase than the pointless one of trying to "develop" her negligible channeling ability.
No other novice was "a future High Seat... who they would have suspected would be next in line to be Queen should anything happen to the Daughter Heir." But, again, that means the Tower was far better served "developing" that relationship than her negligible channeling ability. Failure to learn control would not have killed her, because she was no wilder; it took all the Towers experience in training to get her to grasp the Source even ONCE, and even that much was something she NEVER AGAIN managed (nor probably even TRIED) before Malden, control or no control. It is not like she was at risk of inadvertently/irresistably embracing the Source had they released her immediately, let alone burning herself out or killing herself or anyone else. She stayed a while and got close personal attention, but for purely political reasons.
That would not follow even absent the preceding, but certainly does not WITH it.
Cadsuanes assumption Sorliea equals her age is not a total guess, but is totally WRONG: Even if we accept that 150 estimate Caddy was off by a factor of 2. And from what we know of Sorileas family and that harsh but vigorous Aiel lifestyle it is VERY unlikely she was 150, else she would almost certainly be a great-great-great-great-great-grandmother: SOMEONE in the clannish Aiel society would have remarked on that at some point; instead, IIRC, there was a mention of a great or great-great-grandchild. Assuming she and each offspring bore a child at 30 (middle age for Aiel) that would put her upper age limit at 120. Ancient, sure, but not unnaturally; the main role of slowing there is she is not already an invalid by that age.
Sorilea looks and acts, at most, two-thirds her chronological age; Morgase appears little if any older proportionately, despite having only ONCE channeled for SECONDS, which is FAR less than even the weakest member of even a group that channels little. And we know that not only strength in the OP causes slowing but also USING it, so Sorilea would be far more affected than Morgase even if they were equal (particularly since she has not only channeled more, but been doing so at least TWICE as long as Morgase has been ALIVE.)
There is just no "strong" argument for a significant (if any) strength difference between the two characters held up as the WEAKEST of their respective cultures. Even if SORILEA were the weaker one (which, to be clear, I do not believe) she would still be able to DO more for the same reason Lanfear tied the far stronger Rand in knots in their early meetings: Because of far more training and experience. In terms of secondary indicators, however, there are none suggesting Sorilea is appreciably stronger than Morgase. Given their similar channeler and thus narrative roles, that is understandable; the point of both is illustrating even women who could use the OP did not require it to exercise commanding effective leadership.
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