Amber and Anna are your stereotypical low level chav bullies at school. The arrogance of Amber saying something along the lines of "just by looking at her, i'm better than her in every way possible" on top of the "dead ting" too.
Anna is repulsive in her attitude - the whole "byebye byebye" thing a few weeks ago that Jordan called her out on. Plus the bitchiness of the women on the balcony when Maura and Elma came in.
Some posters like
@altodevil will excuse Amber's behavior somewhat, but she's so snidey / self-entitled and stuck up, that under that "banging" surface there's no substance. Compare to Joanna and she's a bratty child.
The only thing Michael did wrong was probably telling Joanna Amber's flaws so quickly, but you could see that every time he tried to raise it with her, she'd be offended at being called out and either scoff / abrasively laugh it off, or try and remover herself from the conversation. Anna used similar tactics when she had a go at Jordan for calling her embarassing/childish and said that she "had to make it up to her for the rest of the day."