I am a single mother to DD 14 , she has been extremely challenging for about 2 years. She has major anger issues and has received anger management to no avail. She sees camhs but won't engage with what they offer her.
I have fought her corner every day for years with school, with fall outs with everything but I am now at my wits end. She speaks to me with utter contempt , she humiliates me on purpose , she always wants more and is never happy, last night I allowed four of her friends to stay over. She shouted and swore at me when I refused to let them out at midnight and has spoke to me like utter shit ever since, in front of her friends then when I leave the room she's giggling with her friends. She does nothing to help herself let alone ever lift a finger around the house or do any homework. They scratched the hell out of my new dining table last night when I challenged her I just got a screamed sorry. She's never sorry, nothing's ever her fault and she has literally broken me today I cried (never do) and she just stormed out. I have no help with her my family find her so difficult they won't help and I've stopped even telling them or my friends. I'm not sure where I went wrong I reward good behaviour , sanction bad but she is so consistently challenging she does not care and just threatens to harm herself if I ground her , remove her phone etc. I still do but have to physically remove it and she battles for hours to keep it. On the odd occasion she's polite to me it's usually to ask something unreasonable like last night "sorry I've been so rude to you recently I'm just angry I don't mean it I love you , can you but me a bottle of vodka everyone else has one and your the only mum who doesn't buy it" 
. Then I say no then we are back to "whatever your such a jar don't talk to me I'm so angry".
The behaviour has increased in the last couple of months previously it was 50/50 now it's more like 99/1.