I was at boarding school with someone who must have had something similar. I am bit older than Sophie.
The girl I was at school with though, had been told from early on. She was quite matter of fact about it then. Just used to say that when she was born, her parents had to decide if they wanted a girl or a boy, 'so I had my penis removed' and 'I will never be able to have children'. We were about 12 or 13 at that point.
It was only with age that I realised she had probably had a DSD, and was probably technically a boy. I always wonder where she is in life. And how much she understood about it as she grew up, whether she now knows her chromosomes etc. I hope she is doing well and had better support than Sophie