My cheap 2cents-
The emotional reaction that doesn’t seem to fit the situation indicates that there’s something deeper going on for her. There’s only one way to find out and that’s by having a conversation with her. If she was previously partnered with an alcoholic, my wild guess would be there’s something there. She may perceive that now the floodgates have opened with the decision to pay for alcohol for your kids meals and she may fear where that is going. She may have been simply triggered by seeing the alcohol on the counter. To me, without any information, discovering by surprise out that my husband purchased alcohol would be jarring to me, and that I have always felt safe in our sobriety.