isfp 9w1 needing advice with infp 4

hey guys,

I am an isfp 9w1 sx/so and I have been having problems with my relationship with my infp 4w5 sx/sp cousin. we in general don't have a great relationship and I understand that I have my own mental/toxic problems, but she is starting to take everything in our relationship as a competition when I tried to communicate that this behavior of hers is bothering me she keeps saying that she is matching my energy and or goes quiet and says opening up to me would cross my boundaries. I have heard her countless times talk behind my back with my other relatives about making fun of the stupid decisions I made in life ( isolating due to bad depression) even when I am in the house. I have had many conversations with her in the past that have brought me to tears, she would go straight to attacking my lack of character, and authenticity and that I am unable to form lasting relationships, constantly saying the phrase " I have my doubt that your even a good person, it's just a gut feeling".I have tried to distance myself from her but then she would have this thing where she would take to me in a condescending tone and when I snap at her she retaliates. I am open to any kind of advice as idk what to do. thank you for reading my vent.