Obligatory first post... so my fiancé and I have been together just over two years and living together 8 months. SD is seven, was 5 when I met her. I didn't have a lot of interaction with her until i moved in together but all of it was positive, she's a great kid. There was understandably some behavior issues when BM moved out with her, and of course COVID interrupting her routine even more didn't help. All summer was pretty good, SD seemed to like spending time with me when I picked her up from daycare once a week or so. Biweekly visitation at our house was fine. The last few weeks though, this sweet kid has turned into a complete demon. She's had some behavior problems before so this isn't totally out of left field, but has gotten drastically worse. This past weekend was the worst yet, and I don't know how we're going to deal with this going forward. My fiancé agrees that her behavior is unacceptable and has disciplined her when appropriate, and backed me up when I discipline her. Since I'm not really a parent I don't know how to handle this, but I do know that it is not normal and is complelely unacceptable. SD often flips out into temper tantrums over seemingly nothing, and afterwards apologizes and doesn't know what set her off. I'm talking foot stomping door slamming nasty faces... the works. Ignoring her doesn't seem to help, and we've been sending her to her room to calm down, which does work but it's such a fight to get her to do it. We participate equally in the direction to go to her room and my fiancé takes up the talking to her afterward. As for things that set her off... videogames, which she often loses privileges for, and even things like cleaning up after herself after meals, and not leaving toys all over the house at the end of her weekend stay with us. This weekend she flipped out because I had put my fiancé's childhood stocking up as a decoration. She spent the weekend essentially terrorising us, and we didn't get anything done because she was constantly pitching fits. I don't know what to do about this, but it is clear to me, and I think to my fiancé as well that this child is unhinged and has some serious mental health concerns. My relationshop with my fiancé is strong, but I'm not sure how much of my concerns I should bring up. It doesn't feel like my place to criticize SD's serious issues, but it feels like there's no escape... I can't even leave the house on our weekend because of COVID. I will be seriously concerned for our safety if this behavior continues as she gets older.