Probably the best advice is to try and juggle her in the air. Being a Zelda main, it is very hard to come down on someone once she is in the air. Her dair stinks unless it's sweetspotted, so do her bair and fair, but they probably have more range than pikas aerials. As stated earlier, don't spam jolt, but maybe shjolt so that if she reflects it, you don't get hit, and go for a grab as soon as the animation of the crystal is ended. Use dsmash a lot, she's not great close combat, but she's got a fast dsmash so be careful. Beware of the Uair, kills pika probably in the 90s or even a little below. Zelda is a defensive character, so wear her down, and go in for a close hit.
Oh, yeah, don't spam thunder either, as she can reflect it to automatically hit you for a good amount of damage.