Ok. This is not because of SEN. This is just being nasty, manipulative and disrespectful. You have to separate out what behaviours they can't help and when they are just taking the utter piss. SEN is not a green light to behave appallingly.
I have 2 kids with autism and if they behaved like this, they wouldn't sit down for a week. They're not stupid. They know the difference between right and wrong. We've taught them what is and isn't ok and if they choose to do wrong, they don't get away with it.
The nasty words, pointing and laughing, deliberately making you feel shit? Punish that and harshly.
Make it clear what is acceptable and what is unacceptable. No negative comments about people's appearance, do not say shut up, it's rude, do not swear, do not call me names. Really spell it out. Then punish with whatever she does care about. There will be something.
Want a sweet or toy when out shopping? No, you were nasty to me earlier so I don't want to buy you anything.
Invited to a class party? No, you're rude to people so you can't go. No one wants to be with people who are nasty to them.
Want to go to the park? Nope, I don't want to take you anywhere because you said mean things to me. Specify what she said that was mean and why it was mean.
You want to watch TV? No, you don't get TV time today because you behaved badly.
Pocket money? No, you've lost that this week because of what you said to X.
She's doesn't get to choose whether to 'do' punishments. They happen no matter what she does. Take it away, unplug it, refuse to give it to her, hold your ground. Never back down. If you've threatened a consequence, follow through, never make empty threats.
My eldest doesn't have an Xbox. He used to scream and shout at it and shove his siblings if they walked across the room in front of it. I told him to stop doing it and he didn't.
I told him if I saw that behaviour again, I would get rid of it. He said Oh whatever! In a rude tone with attitude. So after dinner I put an ad on Facebook for the Xbox and I sold it. He came home from school and it was gone.
I told him he had been warned, kept up the rude behaviour over it so he doesn't get to have it. The tantrum was epic and lost him a weeks pocket money and a trip to the cinema.
He has been saving up pocket money for another one for 2 years now and I've warned him that the first time he slips back into old behaviour with it, its gone. I mean it. I won't have that behaviour in my house.
You have to draw the line, make it clear where it is and enforce it as firmly as necessary.
Any good behaviour gets praised and make it clear what she did well and why.