My sister is being a dumb bitch rn🙄

My sister is 9 weeks pregnant at the moment. The baby was planned but in my opinion my sister isn't mature enough for a baby. But I still supported her and I was happy she was pregnant. Well now my sister is planning on showing up to this girls apartment to fight her. And you want to know what the reason is? A Facebook post. They may or may not have been directed at her. To me it seems like what was said in that post could have been directed at anyone but even if it was directed at her, she's willing to risk her baby over a petty Facebook post. Like we are in our 30's! This isn't High school. Not even high school I'm gonna day Junior High. I've been trying to talk some sense into her and I told her to just worry about her baby. I told her if the girl doesn't fight her she could call the police because my sister would be trespassing and if she does fight her she could lose the baby. Well my sister said "I don't give a fuck. I'm gonna fuck that bitch up. Blah blah blah." Then she accused me of taking the other girls side. This is why I said I never thought she was mature enough for a baby. She risk losing the baby over a Facebook post, when we are in our 30's is so dumb. So she's planning on going to fight this girl this evening and I've tried to talk her out of it. I don't want her to lose her baby. This whole thing is just immature and stupid! And this isn't even just hormones, my sister would always fight people for dumb reasons. She used to tell my younger sister to go tell some girl she thought she was ugly just so she could fight her. I just figured she would not want to do that while pregnant.