@TheKingStrategist13 Because he already knows what Leo is capable of, which doesn't include magical threads that can mind control you to do whatever the user desires, so he can get away with it on top of the fact Leo was exhausted fighting a Kefka clone.
@Hypertornado099 Freezing via status ailments which isn't the same as imagining she gets frozen into a block of ice that can shatter into a million pieces. Two completely different applications here. Also him knowing about the mind control spell she has would incline Kefka to keep his distance. He's not an idiot and wouldn't underestimate his opponents, otherwise he'd have done so against Leo of all people.
@Follow_Doctor_Freeman the cross continental beams isn't really what I'm referring to, I'm referring to any of his normal magic spells since even during Dissidia when he fought Tidus and Vaan and he's flying from a great distance to spam magic against them while he's in his normal state. Reality warping resistances doesn't help resist Subjective Reality given their applications can be completely different from one another. Same reason why we treat Madness and Mind resistances as separate things.
Also hey Freeman, been a while.