The best advice I can give is to tire that kitten out before letting her interact with Ralphie. Play with her until she’s totally tuckered out. That should keep her from wanting to get rough with Ralphie and make things go a lot smoother. Also, clicker training worked very well with my cat, although she was an adult when we got our bun. Reward her for being calm and relaxed, if she gets into this hunting mode (staring, stalking), you should put a stop to that right away, don’t wait for her to actually pounce or chase. Clap your hands, or make some kind of noise to snap her out of it. Then reward her again for calming down. If she does pounce or try to get rough with Ralphie, remove her from the situation and get some more play time in before trying again.

Good luck with your kitten, I bet they will be great friends. My cat and bunny get along just fine even though she’s pretty high strung. She learned what’s acceptable around the bunny and what’s not.