A step in the right direction
Today I disengaged completely from all the kids not just SD7. I also did zero around the house. Dinner was canned stew stirred through some rice. Everyone had to wash their own plates and cutlery because none were clean. I said I wasn't hungry and left DP to handle the kids. It opened his eyes to how much I do around the place and how much effort goes into parenting the kids.
I want to point out that he thanks me daily for all that I do and tells me I'm amazing and all that stuff. We own a business that we're in the middle of making changes to so that he can have more family time.
He found out that all the kids had been asked multiple times to do simple tasks and hadn't. SD7 was trying to act all perfect in front of him, but the fact her hair was halfway to dreadlocks proved she was just as guilty. So he made sure they ate All their dinner, he made them clean up the kitchen, dining area, and bathroom, and he got them off to bed. He had to deal with detangling the almost-dreadlocks.
I think today opened his eyes to how poorly behaved and dismissive of me his little angel really is, and the effect her attitude and behaviour is having on the entire family.
Yesterday we took the family to a trampoline park and he saw first hand why his little angel doesn't have any friends. SD7 latched on to a 5 year old girl she'd never met before and started bossing her around. At one point she had the girl pinned up against a wall and was talking very animatedly into her face while the girl cowered. Then she grabbed the girl by the wrist and dragged her across the length of the park while the girl was trying to get away. DP went to intervene and while he was walking towards her he saw her rake her fingers across my BS8's throat as she clotheslined him. Later she joined in a game of tag with some other kids but when she was it she'd full on punch them, usually in the face. She would also repeatly "accidentally" kick kids while jumping on the trampolines. He couldn't blame her behaviour on anyone else. The scales are finally falling from his eyes and I don't think he likes what he's seeing.
TLDR; DP is realising his little angel is actually a little demon and she's turning my kids into demons too.