Forget about restaruants..... A much more important way to start being more dominant would be to refuse to be her punching bag. If you stay around and cop her foul moods, then she's absolutely right that you're lacking in balls.
Next time she turns her temper on, don't try and calm her. And don't yell back at her. Simply tell her that her behaviour is unacceptable and walk out. And don't return until she apologises. Do this every time she's acting appallingly.
Word of warning though, yes it may well ease when her job stresses end. But unless she addresses her own issues, her temper will return when she next gets stressed out. This ISN'T a one time blip in her personality.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.