Some people seem to have strong emotional reactions when it comes to weddings. The weird thing is that it doesn't even have to be their own weddings - just being in a wedding is enough to make some people feel insecure. Which is exactly what happened to the girl in the above photo - the groom and bride were having a picture being taken, and in the background, you can see actual cake coming out of her mouth.
Just imagine her surprise when she saw that there was a photo of her like this - she probably got even angrier with the couple for publishing the photo (if it even is the couple's fault - perhaps the photographer submitted the photo to social media without them knowing). Although it's not like she needed an excuse to not like the couple - she already looks to be pretty "disgusted" by them.