Why did Eve sin?
Here's the answer:
Satan deceived Eve by lying to her and she chose to sin.
In the garden of Eden, God said that Adam and Eve should not eat from the tree of the knowledge of good and evil (Genesis 2:16–17). Satan came along, disguised as a snake, and he tricked Eve into believing that if she ate of the tree of knowledge of good and evil she would be wise just like God. Eve believed Satan so she ate the fruit, and she gave some of it to Adam to eat too (Genesis 3:2–6).
As soon as they ate that fruit, Adam and Eve were separated from God because God is holy (perfect) and can’t be in the presence of sin or evil.
Satan tempts us too. Sometimes people believe Satan’s lies instead of God’s truth. In fact, the Bible calls Satan the father of lies. When Satan tempts us, we can say no to the temptation and yes to following God’s way.
"You belong to your father, the devil. You want to obey your father’s wishes. From the beginning, the devil was a murderer. He has never obeyed the truth. There is no truth in him. When he lies, he speaks his natural language. He does this because he is a liar. He is the father of lies" (John 8:44).