My sister diets to get atttention?

She is really skinny but has NOT lost any weight visably yeat she has done this for nearly a year . Like for dinner she said mummy I am really full I don't want much like literally less then half a bowel. Then my mum said ok pour it your self and she just poured the water from the soup none of the vegtables of pasta. And i brought a bag of sweets and she kept on calling me fat and refused them saying ewww no. Then five minutes later ate loads ughhh . SHe said she was going to run every day after school cause she isn't fit. Yet doesn't go running with my mum or I but she always talks about how she is going to go after school .