Co parent issues

I my ex and I co parent my son, she also has two children who I am in no way responsible for. I live 30 minutes away and today she called and stated she was out of milk and diapers! I said if you have time to go on dates you have time to sock your house with essentials. So she got mad, would not have a phone conversation and hung up mid call, wtf how is this a "me" problem