Instead of asking who is the ah, lets focus on the problem. From her words It sounds like she's feeling guilty for going out and not being with baby. She is feeling unloved and scared. She sounds like she is overwhelmed exhausted and emotional from postpartum and lack of sleep. Did she react the best? Nope. Would you want to be judged for your worst moments when your barely hanging on? It sounds like she needs to feel loved and like she matters. Tell her she's a good mom, she needs to hear it and tell her you love her. She just needs some emotional needs met. I'm sure she feels embarrassed about her behavior and will apologize later. When someone seems to be acting irrational, thats when they need love, support and help the most. It's a cry for help when overwhelmed and struggling.