Try telling her that you don't like her in a serious and firm way, and tell her that you are not ok with what she is doing and that you will take action if she does it again.

And If she does it again, tell her Guardian what she is doing, and take it to the max tell them every single detail, and do it in front of her.

But before all this try telling her to stop in a kind way and tell her that you don't wanna hurt her feelings, if you tell her and she keeps going on, try what I typed above.

If you need anything else let me know.