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This is what I think. She only side with her at the beginning to get to the glasses girl that resigned. She didn’t like that she was acting all big in front of her, she is the boss and the glasses girl works for her so why is she acting all big. Glasses girl got rid of tangs application and was doing shady stuff. So she got the other guy and tang which were people the glasses girl hated and did a in your face, you think you can control the boss, well think again. But Now, she is noticing she can’t control tang and is seeing her as a threat..... I think. She doesn’t like that Tang does things without asking for permission and causes problems within the agency and models and she didn’t want to go eat with the red head. So she trying to get rid of someone who acts on her own and isn’t a puppet she can control. I may be totally wrong but I got that impression.
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Exactly, she was shown as controlling character in the novel. She was mad at tangning and was against her bc she wanted to control her, gain popularity by whatever she says (eg., going on dates w popular celebrities she set ) and make tangning her puppet who does whatever she says. And that was the reason that she signed tangning as well. But she came to know that she won't be in control of her, so she started going against her, by defaming, kidnapping, and what not. She sees tangning as threat to her ego of an ceo.
I still don't understand why the purple hair woman got against Tangning... like she was beside her in the beginning and now she wants to destroy her career wtf???