According to the ASPCA website, the Christmas Cactus plant is one of the few plants that are not toxic to cats. Before you bring any plant into the house, take a quick look at their website to see if the plant is toxic to your cat (because most plants are): https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants. If you really want to keep the plant, you can try spraying the plant with diluted Cheyenne pepper or hanging the plant somewhere your cat can't jump (although they will almost always find a way).
When you make the commitment to bring a cat into your home, you give away a few "rights:" the right to go to the bathroom by yourself, the right to have tinsel on your Christmas tree or ribbon on your presents, the right to have clothes without cat hair on them, and, yes...the right to have plants inside your house.
Regardless of the few things you give up, I'm sure you will agree that the friendship and love you get in return is well worth it!
It's innate. Cats chew plants. It's really much easier to get rid of the plant. There will be no more "getting on to" your kitty and no more seeing how much of a bite your cat can "get away with" before you notice. I think you will find that a plant-free home will be more peaceful to all involved.