Rush Chun before she gets her meter going. Dive pressure is free of charge since she has no reliable anti-air options before she has meter. Mydingling pretty much stated it properly.
If she’s doing neutral jump HK, stand outside of the range, and you can counter with C. HP (I believe) and cannon spike, or just start your own jumping TK-Cannon strike pressure after you hit her, or after her jump Hk whiffs.
You can focus bait her crouching HK and punish heavily. You can also focus Hazhan-shu. Applying pressure is the best strategy. Chun doesn’t have much vitality and Cammy hits like a ton of bricks. If you’re going to try to outpoke her, do it carefully since she’ll outprioritize you head on. Counterpoke wisely.
If she’s grounded without meter, mix up with throw, dive kick pressure and hit confirm C MK xx HK spiral arrow. Always watch for EX-SBK on wake up if she does have meter. As Dingling said, bait that shit out.
And don’t forget Cannon spike, far standing RH, and Crouching FP if she tries jump-ins on you.