You ask Moondancer if somepony who isn't a unicorn would be able to cast the spell.

Moondancer: "Yes. Here, the book says any pony can learn this spell. Look."

Moondancer opens the book in front of you. The book reads:

"Dispel Strike. For the strength of a pony's hooves to dispel the arcane. Speak the magic words:

Let my hooves lay magic to rest."

Moonflower: "Ooh! Fightin' with hooves' your thing. Maybe you should learn it!"