Discrepancy in lore (spoilers)

[Bhearil]

That doesnt work when you have literally an army chasing you or battles would be won by a single mage casting grease and making the enemy army slip and keep falling. She probably used some tricks to earn some time but there were literally too many soldiers, plus we dont really know the extent of her powers on that moment, and in any case those tactics doesnt make you inmune to ranged atacks (actually Thancred got an arrow to the knee if remember well).

Also if she would have frozen a larger area of water would have meant they would have been caught as well, their legs trapped in frozen ice. That mages due yo gameplay reasons cant eat their own spells doesnt mean that lore wise on confined spaces wide area of effect effects arent nasty. Either the effect is too small and thus irrelevant outside of trying to get extra distance, or is too big and they got caught in it since they were on a tunnel.

Many DMs will grin when some player has the "brilliant" idea of using aoe spells in closed spaces and kill half of their own party alongside themselves