Why does my sister in law humiliates me in front of everyone "jokingly"?

I hate it she's gorgeous i dont what I've done to her she always comes off as a hater and jealous her brother which is my boyfriend even laughs at me when she insult me like its a joke when its not. It hurts my feelings and she literally makes me sound like im stupid because she also made a comment on that and he laughed.

Why does my sister in law humiliates me in front of everyone "jokingly"?
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