Why does she love to bring about negative events?

My sister always comes to me with negative thoughts… for example, she says our family is cursed… sometimes when I'm finally trying to be happy, she asks, 'Does your husband like us?!' She asks me if my husband likes our family!! Why shouldn't he? The more often he asks me the question, the more likely it is that he really won't like the family anymore because they always assume the worst.
Then one day later, when he was sleeping with me, she asked again, 'Aren't you annoyed with us? Aren't you sick of spending so much time with us?!' … (She asked because she knows it differently from her husband, who doesn't want to be with us after five minutes.) And then my sister always brings up negative topics of conversation and says to my husband at the dinner table, 'We're crazy, we're a terrible family, we're nuts…' and it always goes like this with comments like that!! My husband doesn't even think that far, or rather, he doesn't think anything negative, he's doing really well, and then he always wonders why my family thinks in such strange ways…

I can't take it anymore… it's destroying me mentally to always be confronted with negativity, especially since other people don't think as negatively as my family… my sister shouldn't be surprised that at some point nobody likes her anymore and she's left completely alone because she's basically manifesting it!!

My husband now thinks that everyone is crazy, but only because it was brought about and people were pressured to think that way… at some point I won't be able to visit my family anymore because it's all about religion and negative topics!!