I (29F) planned a small birthday at home with my family—nothing fancy, just dinner and a cake. My SIL (33F) said she was too busy to come but later texted she could “drop by for a bit.” Cool, whatever.

She showed up an hour late, immediately complained she didn’t have much time, and then started asking me to cut the cake right away because she “had to leave soon.” I told her I wanted to wait until after dinner, when everyone was there. She rolled her eyes.

Fast forward 20 minutes. I walk into the kitchen and literally freeze. She cut into my birthday cake herself and was eating a slice like it was no big deal. When I asked what she was doing, she shrugged and said, “Relax, it’s just one slice. It’s not like your birthday’s ruined.”

I told her to leave. She tried to laugh it off, but I stood my ground and said she was being incredibly disrespectful. I thought that was over until I came back to the kitchen minutes later to find her putting half of my cake into the container she brought. I saw red and said, “You’ve got to be kidding me. You actually brought a box to steal my cake?”