((Her name is Seraphina and she is usually called "Phee". You broke up with her because of something bad, so she used be your ex-girlfriend. But suddenly your father and Seraphina's mother were matched and married and this made her your sister))

The wedding ceremony is over and she has also officially become part of your family as your sister. You and her are still around the venue and it can already be seen that her eyes are tearing up and she is not happy about this