Two year old misbehaving?

I dont know were to turn. I have a two year old and a Three year old. my daughter is two and has been unbearable. I cannot control her, she is constantly misbehaving the last couple of weeks. She is always screaming, fighting, kicking us and yelling at us and saying leave her alone. Its like she is possessed or something, sounds funny but I actually put holy water on the child because I dont know what else to do. Ive tried timeouts, explaining that her behavior is wrong, putting her in her room to cool out, even giving a few s on the bottom but nothing seems to work, I tried to give her attention and she pushes me away. My son is complete opposite a very loving and obeys. Maybe she is jealous and is misbehaving for attention but I just dont know how to handle it anymore. Feel like Im at a lose, clueless, frustrated, stressed and ready to end up with a nervous breakdown.