A childhood belief about imaginary friends

When my sister was little she had an imagery friend called Roger n she used to sit in her room for hours talking to him n playing schools n stuff like that. My mum always thought she was wierd n kept trying to tell her he wasnt real but she wouldnt have any of it n continued to play with him. Eventually he left, he moved to America i think, n my mum was really happy that shed grown out of it. When my sister was 6 she came home from school n told everyone that Roger had started school and was coming for tea, my mum was horrified n kept saying he wasnt real. But it turned out Roger was actually the name of a boy who had just moved to my sisters school and he did come round for tea.