She's a grown adult and does have a right to do what she wants to. You should have waited later and then told her what you knew and that you would have appreciated if she told you she was going out like she said.
Is that a rule with the two of you that she has to tell you when she goes out?
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.