My 6 year old constantly has an attitude how can I fix it?

My daughter recently has been starting to have attitude problems one minute she’s happy and the next minute she’s whining or has an attitude. Some examples are If she ask me a question and I take more than 10 seconds to respond she’s stomps away and goes in her room. Every time I make her food she waste all food and ask for more food a hour or 2 later so I tell her to wait and after 5 minutes of waiting she starts to cry get mad or mumbles stuff under her breath. And if she ask me for something and I tell her no she gets mad I have never had this problem with her before how can I fix our relationship?
My 6 year old constantly has an attitude how can I fix it?
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