Girls, hello. Help me with advice, I don't know what to do anymore. My…

Girls, hello. Help me with advice, I don't know what to do anymore. My eldest daughter has been staying with her grandmother (my mother-in-law) for a month now. Since she came back, I don't recognize my child. The mother-in-law spoiled her so much. She does whatever she wants, and it's impossible to say no or she ignores you, or screams at full volume. Even at night, she wakes up and screams. I don't know what to do. She's constantly having tantrums. She only eats while watching cartoons. I can't take it anymore. My husband is also shocked. Our child was never like this. I try to give her