S.,
This is going to really sound harsh, but I think the reality of what you are doing to your child, unintentionally or intentionally, has a major impact. You really need to think about the message you are sending to your child. Packing her bags is confirmation of what she already feels and doesn't understand why, and it doesn't matter if she made it downstairs or not. That is not to be taken lightly. She is trying to send a message to you the ONLY way she knows how to at this age. Your actions are completely inappropriate and mean spirited. You are suppose to be the grown up. I have 5 children and not one has ever told me they hated me! I would be mortified and devastated, but I would also be trying to find the root of the problem too and deeply reflect on myself as a parent! So not everyone does go through it. Please do not live in a world of this happens to everyone, because it doesn't. I am sure my kids have not liked some of the decisions I have made for them and been REALLY upset with me for making them, but NEVER have they told me they hated me. They might say something to their siblings or friends, but that I don't know and nobody has ever said anything to me. :) I am not saying I was the perfect parent because I was NOT, but I did make sure our home is and still is a safe haven for my family where NOBODY can hurt them. There is enough hurt in the world that they do not need to endure it at home too.
You say your 4 month old son has you "wrapped" around your finger.....What about your daughter?!?! I have 4 girls and 1 boy, so I understand your feelings, but the others need just as much of me. Boys are truly special, but girls are too!! Maybe she's "feeling" the difference not so much in words, but by your actions.
Hug her.
Comfort her.
Listen to her.
Kiss her.
Make her feel secure.
Make her feel safe.
Earn her trust back. (You broke it with packing her bag! That is a breach.)
Take her out for a special day alone together.
Reassure her.
Make plans with her and keep them!
Correct her in love.
Let her know she hurts you and she needs to take a time out to think about what she has said.
HUG HER AGAIN.
Let her know daily how much you care for her, because you do not want to have any regrets if something should ever happen and you have to live with yourself.
Hope this helps......I don't really beat around a bush when it comes to children. They are VERY important to me.
Blessings,
M.