Damsels and Prophetesses are powerful individuals, for in their years away from Bretonnia, their innate abilities have been honed and tempered. Their magic is orientated around nature moreso than most other human Wizards, for they are taught by the handmaidens of the Lady. Riding into battle, Damsels and Prophetesses use their powers to lend magical protection to Bretonnia's noble warriors, warding away the foul magic of their enemies as well as casting them down with powerful spells of their own. They are also able to mystically encourage the landscape to fight the Kingdom's enemies; persuading the trees themselves to lash out at the foe; calling flocks of birds to descend on the enemy at their call; even drawing lightning from the heavens to strike down in devastating arcs.
The buffs from the Lore of Beasts synergize well with the emphasis on cavalry in the Bretonnia roster. Pann's Pelt allows them to catch up to enemies faster and provides physical resistance (Bringing the physical resistance of Grail Knights or the The Companions of Quenelles (Questing Knights) up to 42% which is nothing to scoff at). The cure of Anraheir slows opponents down for your knights to catch them and lowers melee attack, meaning more damage dealt. Wyssan' Wildform also provides some armour (which is not super helpful, but still helps somewhat) alongside weapon damage which is perhaps better when charging infantry to deal more damage than in a pitched cavalry engagement where the playing field (and the enemies armour) is more even with your own knights.
Transofrmation of Kadon is also a forever useful spell that is very easy to get value out of and distact your enemies so that your knights can swoop in.