My dd is 9 and recently she’s been going in the huff for everything. Stamping her feet, slamming doors and just being ridiculous. Is this the start of teenage years? She jumped on her sister who was hiding knowing that she was there and hurt her. She immediately pretended that she didn’t know she was there and when I just said for her to be careful she went in a strop and blamed her sister for her hurting her. I didn’t tell her off or yell at her but she made a big drama out of it all. That is just one example. It’s now resulted in her not wanting to playing with her sister and telling her she hates her. She even pushed her when she walked past her. How do I handle this?