Yep, it is very possible that anyone can learn to shoot fireballs against these creatures. Apparently fire is their main weakness so any source of fire will be more than enough to burn these leaf monsters to a crisp.

(There are more monsters coming out right about now and Isabela in turn flings more fireballs at several of the monsters, causing them to combust real fast. They try to run away but the rate of the fire burning proves to be too much for them as they collapse on the ground.

Those who didn’t got burned by her fireballs but saw their fellow leaf monsters burn scream for their lives as they try to run away from them.)