Girl in the mirror

Karkat Vantas once said, "The past me is was always so terrible, even when I literally just finished being him.” Every time I look at into the mirror, it reminds me of the past. So today, I’m going to share the stories of the girl in the mirror with you---how she became spoiled, arrogant and mature.
At first, a little girl appeared in the mirror. She was tiny and skinny. Her face was pale, and her voice was weak. She whispered to me that in the school, her teachers and friends treated her like a fragile doll; at home, she was the apple of everyone’s eyes. Because of her adorable appearance, she could get whatever she wanted. She felt like a princess, who deserved all people’s everyone's love and care. But I thought she was just spoiled.
Later, the little girl disappeared and there came a teenage girl came in the mirror. She wore a heavy make-up and got drunk. She shouted at me that she was running away from home because it was party time. Never did she stop hurting her close friends and her family with her mean words. Because of her sharp tongue, she always blamed others and felt good about herself. She felt like a queen, who conquered the whole world as the supreme leader. But I thought she was so arrogant.
Finally, the teenage girl was gone too, leaving another girl in the mirror. This girl looked exactly like me. She told me that she realized her faults and regretted what she had done to all the people around her. I thought she was more mature and responsible. I knew she cared and wanted to turn a start a new page of her life. Why? Because I’ve been that girl in the mirror all the time. No matter who, the spoiled one, the arrogant one, or the mature one, they've all lived in my past.
As we know, no one is born perfect. However terrible the past me was, I would accept it without any regrets. And I hope you would do the same thing for yourselves whenever you look at the girl in the mirror.

Very nice story. I like the Homestuck reference at the beginning. You mostly had grammatical mistakes, but you're doing very well. :)