Watch Your Words
Put out the flame of blame. The next time you need to discuss a problem, be direct, and directive. Let the other person know what's bothering you. Tell her what you want her to do differently.
Leave "you" out of the conversation. Instead of saying: "You always go ahead without me." try providing direction in a kinder and gentle way: "I'm disappointed that you left without me. Please wait for me next time so we can go together.”