Dog experts help! We have really spoiled our little dog rotten. Is her behavior reversible?

I know that we have done all the wrong things out of love for her. I got her from a dog shelter and felt sorry for her. So we lavished het with love and attention to the point wher she does what she wants and pays no attention to instructions. Always wants her own way and gets upset when she doesn’t get it. She is just over 2 years old. Are we stuck with a disobedient dog or can she unlearn things?