Why do people have to ruin parties?

So my sister-in-law comes to my Christmas Eve party toting a container of kiwis and squash soup. Kiwis and squash soup have no place in my traditional menu of spiral ham, tortellini soup, and other appetizers such as meatballs and veggies. And then to top it off, she just sets the kiwi and squash soup down like "hey, do something with this random stuff I brought over". Same sister-in-law ruined our grab bag game by announcing that we were not allowed to steal gifts this year. What fun is that and who put her in charge?