Many good responses here, most humorous. Fair warning... these aren't funny:
You know she's upset when she calmly suggests that you might be more comfortable living in the garage.
You know she's upset when she assumes the worst about things she knows little or nothing.
You know she's upset when your efforts at reconciling are summarized as "your rules".
You know she's upset when you tell her the truth and she calls you a liar.
You know she's upset when she asks you to move out.