Her brief description of her Tower "training" indicates ITS brevity: Stating it took hours of frustration just to grasp the Source ONCE strongly suggests that was the ONLY time she EVER grasped it, and the LAST the Tower ever bothered with even perfunctory "training." Since the AS knew her ceiling the moment they saw here (so precise reports of it probably arrived before she did) they also knew she could never be even an accidental threat to anyone even if she managed to grasp the Source every time, which she almost certainly would not: They did their due diligence, such as it was, for diplomacys sake, then sent her on her way. Her time there was more about learning the Towers way than the Powers.

As for outward physical signs, Sorilea does not look YOUNG, just no older than somewhat younger Bair, and the books do note Morgase retaining her youth more than one would expect, so that difference is also negligible.

The main difference is that, though channeling was not a primary WO concern, Sorilea almost certainly got FAR more channeler training than Morgase, simply because it was practically impossible to get LESS. She probably got more "training" and "practice" trying to wave a kerchief throughout ONE AFTERNOON than in the whole REST OF HER LIFE COMBINED. The mere fact Sorilea can grasp the Source at will shows more training than that; it does NOT necessarily show more strength.