What are Abigail's feelings toward John Proctor in The Crucible? Why is she antagonistic toward Elizabeth Proctor?

Abigail is a selfish vindictive girl. She wants to feel like she has power. She is a bully and threatens her friends to keep quiet about the truth.

Abigail had become the housekeeper for John and Elizabeth Proctor. She and John have an affair, and when Elizabeth finds out about this, she fires Abigail. Abigail is furious at Elizabeth. She claims Elizabeth is spreading lies about her around town. Abigail thinks she is in love with John, and is convinced he feels the same way. 

"I look for John Proctor that took me from my sleep and put knowledge in my heart! I never knew what pretense Salem was, I never knew the lying lessons I was taught by all these Christian women and their covenanted men: And now you bid me tear the light out of my eyes? I will not, I can not! You loved me, John Proctor, and whatever sin it is, you love me yet!" 

After Abigail says this to John, he tells her he has no feelings for her. Abigail then sees Elizabeth as the woman who has everything she wants. Abigail concocts the entire story of witchcraft, to have Elizabeth executed, so she can marry John, and finally have everything she wants.