......and for the record, I am not saying you messed up like my ex does. He just puts himself first all the time. You had a legit bad morning. I had one today and I didn't even handle it so good. It happens.
You can indeed say " I understand you didn't approve of so and so, but I appreciate it if we could discuss this and leave the kids out of it, as it is an adult conversation."
Those things are certainly acceptable to say and may find she didn't even realize what she did was wrong. Try this before you write her off like cancer:)