Originally Posted by Furious_Female

Her hormones might be altering her moods, but there's an underlying problem. I doubt her sadness started yesterday. She obviously feels neglected by you and needs more attention. She didn't freak out because of one day... I guarantee it's been building up for some time.

Give her some special attention... make her feel loved and wanted. You might know you love and want her... but when you are busy working and don't get as much time together, she might need the reassurance.