I'm saying that I'm a moody, insecure, narrow-minded, jealous, borderline homicidal bitch, and I want you to promise me that you're okay with that, because it's who I am, and you're what I need.

This quote is saying that the speaker is a difficult person who is prone to feeling negative emotions such as insecurity, jealousy, and anger, and they want to be accepted for who they are despite these traits. They then emphasize that the person they are speaking to (you) is what they need.