My SIL uses her kids to threaten and manipulate her family members

My SIL (23) has 2 kids (2 and 3 year olds) and constantly uses her kids as tools to get what she wants. I've seen it so many times.<br><br>Once, my husband (27) and I (26) had plans to go out for dinner, but my FIL (50s) asked us to come over to his house because my SIL was going to be there and he wanted someone to watch her 2 kids because my SIL's mental health was not doing well and she wanted time to herself.<br><br><br>So we went over and my SIL immediately went to her bedroom to be alone.<br><br>My BIL (25) was also there and he said we should play board games. My husband, my FIL, and I said it was fine, but my BIL insisted that my FIL go to the kitchen to make some snacks for us.<br><br>My FIL said he was tired and didn't want to make any snacks, but my BIL kept insisting. So my FIL said "fine, but don't wake up my granddaughter" (SIL's daughter). My BIL said "maybe I will, maybe I won't" (he was joking).<br><br>My BIL went to the kitchen to make snacks and my SIL came out of her room RIGHT AWAY and started screaming at everyone, saying my BIL was a sicko for wanting to wake up her daughter just to make snacks. I don't even remember my BIL saying anything about her daughter, he just said "maybe I will, maybe I won't" as a joke. It was a bad joke, I'll admit, but my SIL started saying shitty things to my BIL and my BIL started saying shitty things back to my SIL.<br><br>A few months later, my husband and I were discussing our plans for a vacation with my FIL and my BIL. My SIL walked into the room and asked us what we were talking about. We told her about our vacation plans and she offered to dog sit for us while we're away because she loves dogs and my dog is her favorite dog in the world.<br><br>I politely declined and said I already asked my friend to dog sit for us. My SIL said "but I thought you loved me! You know I love your dog!" And I said of course I love you, but my friend has already agreed to dog sit for us so I can't ask you now.<br><br>My SIL ran out of the room crying and my BIL went after her, saying "baby, what's wrong?" My SIL came back and started saying that I'm a shitty person and that I don't care about her or her feelings. She said she was going to call CPS on me because I'm abusing my dog and that's why I don't want her to dog sit for me. My BIL was defending my SIL and saying she was right.<br><br>I don't even know what the hell was going on. I've never seen my SIL act this way before. She always talked about how much she loves my dog and she's always been nice to me, so I don't know why she said all of that shit.<br><br>Another time, my husband and I were talking about moving to a new house. We've been talking about moving for a few months now and my SIL knows about our plans. So we were talking to my FIL about our plans to move and my SIL walked into the room. I said "hey SIL, how are you?" And my SIL started crying and saying that we're leaving her behind and that we're shitty people for abandoning her. I said "but SIL, you know we've been discussing this for a few months now" and she said we're liars and we never told her about our plans.<br><br>tf what is wrong with my SIL?? I've never seen her act like this before. She constantly uses her kids and her mental health to get what she wants and to guilt trip everyone. She's always talking down on people and making them feel bad for no reason.<br><br>**EDIT:** No we don't live with my SIL. She lives with my FIL. He refuses to kick her out because he's a pushover. My BIL lives with us because we converted our garage into a separate living space.<br><br>For context, my BIL (25) said that my SIL (23) has always been a manipulative person but after she had kids, she got worse. I said what happened when she had kids and my BIL hesitated for a sec before saying "I'm not sure if I'm supposed to say this, but I think it's okay to tell you since you're family so... she tried to kill herself when her first kid was born (my niece). I think it was because of postpartum depression or something, I'm not sure" My BIL said that my SIL's mental health got worse after she had her second kid (my nephew).