What are you best idea to make jealous sister in law go insane when she is being direspectful when my boyfriend want to spend time with me?

His sister is sending insulting message about me when she is angry, when her brother is staying at my house and want to spend time with me.
What would be your ideas to make her more jealous or angry, so she stops acting this way when I am with my boyfriend. When he is at mine it is like she is angry that he is at my house and not at their home.
What are you best idea to make jealous sister in law go insane when she is being direspectful when my boyfriend want to spend time with me?
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