Shocking potty mouth!

My little girl , named Angel, just turned 6. She is displaying avoidance of making friends – often commenting on people’s appearance of not being attractive or pretty, that they are “weird” and we are coaching her towards inclusive play but more recently she’s actually started being aggressive in her play by getting one child as a friend on side and whispering about the other child that is larger.
We have had ongoing issues with her saying more aggressive words with the family – ranging from “shut up b*tch” at her sisters and now even at me when I am disciplining her.
Tonight she went to my eldest who has ongoing behaviour issues with reactive words at me – and apparently went to the car and said “I hope you die, b*tch!”
Miss 13 year old came out devastated & asked what I was going to do – she says it’s ongoing and that my children are the nasties children on the planet – It’s hard to know who is to blame as the 13 year old had been tantrum throwing saying “you just want me dead
“ to me & miss 13 does get a bit rough with her siblings at times…

I don’t know what to do! We attempt saying “no we don’t do that and giving extra chores, and tonight I withheld her from having a breast feed (which she still asks for at age 6!) I am praying for them all. I am wondering if Miss 6 has some sensory issues and is dopamine seeking / we had some horrid heavy discipline routine when she was tiny where a coach recommended very strict use of a harness and restrains for anything she did wrong and she has a very reactive streak of lashing out physically with her siblings.
And then she will say she is bored doing regular activity & sneaks off to watch YouTube shorts on any device she can find – which we have said is a no answer but I haven’t been consistent in enforcing except to turn it off and attempt to re-direct.
I am hoping that someone will say – she’s okay & we are on the right path to just correct her calmly& connect with her now – but it worries me that she seems to not be able to connect & even with wanting a breast feed she was wanting at times as a little person to feed from my friends after they fed their babies – I feel like she hasn’t attached properly – how do I know if I am breeding a sociopath/psychopath??