Sister won’t stop bringing toxic/poisonous flowers and plants in the house

Hi everyone. I am asking for some advice on what to do with my little sister.

As stated above she will not stop bringing toxic or poisonous plants and flowers into the house despite me telling her that MY cat is curious and will bite/chew if given the opportunity. She seems to think that just because she keeps them in her bedroom (somewhere the cat never goes and isnt allowed in) that it’s fine.

In the past we have had a scare with lilies due to her negligence. He is fine now but she never took it seriously and continues to bring in tulips and other plants. She got the message about lilies but not any other plant.

She doesn’t understand the risks of even her walking out of her room and petting him can make him fatally sick. Or let alone her just opening her door can let stuff come out. I have told her time and time again that even the pollen of these plants can kill my cat but she doesn’t seem to care.

I am looking for advice on what to do, how to stop her from bringing them in despite her “keeping them in her room”. Any help and suggestions would be appreciated.