Everything is wrong. Why would you ruin her cake when she is happily taking a picture of the dessert you are both having? In my opinion, when a woman behaves like this is when she is sick and tired of a lot of things. Like if a huge mess of problems and things she does not like about you just exploded in front of you. Am I justifying the behavior? No. But it is the most reasonable explanation I can find. Just like when you do something silly and she decides to end the relationship and you think it was because of what you just did, but the real reason was all the things she was saving in her heart and what you did was just the cherry on top that made her take that “impulsive” decision.