Ah, that would be because she's a Persona user, as are many of her peers. There's a surprising number of them out there, no doubt under Shido's nose.

[Ah, but the thought of Mitsuru beckons a soft chuckle. That's a fun little bombshell up his sleeve, isn't it?]

To be honest, she's a dangerous adversary regardless, seeing how she can summon a Persona in reality.