Rotor warping at 24k is extremely premature. She must be a heavy braker..?
(edit: nvm, googling seems to show that premature rear pad wear is a common problem. Did the pads wear down too low causing the warping?)

If it were me I would just resurface them and go easy on the brakes assuming the driver is a no throttle control gas, brake, gas, gas, brake, gas, BRAKE, gas gas brake type. Or upgrade to Brembo Blank rotors and aftermarket pads.

The parts store (assuming Honda Parts) should know. I don't see why they wouldn't. But I'm almost certain the smaller rotor is for LX and larger for EX.