Horrible Day Stupid Niece

I had a horrible day today. My niece (12) had lied to her mother, my sister in law about me. Saying that i “made” her mow tge lawn all by herself when I and her little sister helped. ALL three if us at the same time. She was even paid for it yet told a damn lie like it was child slavery. But its not that its the fact i tried to make her happy, free trips to the movies, free symmer camp, bike rides, trip to the water park, getter her free school supplies, ice cream, candy, staying up until 11 or even one in the morning. All of this i did for her in ONE WEEK yet she still had a nasty disrespectful attitude, ungrateful, and down right mean. I get it shes a kid, but she had no reason to lie on me or stomp over my kindness like that. So i simply took her back to her drug addict parents now my brother and sistsr in law think im a monster. Like i cant fucking win can I? I tried, i truly tried to give her a good happy summer yet she didnt give a shit. Also my cat of 8 years died so im sad about that. And my perfect rich successful little brother is coming home in two hours. So my mother will once again roll out the red carpet for him while complaining about what a failure i am. I honestly dont have anything to live for. Im just depressed and ghosting through life. Even when im being a good person im punished for it. Damn it