A six-year-old girl who has lived in a 'bubble' because of a rare immune disorder can finally play outside for the first time thanks to a live-saving transplant - from her big sister. Little Milly Smith was born with a disease which left her with no immune system so even a trip to the beach or playing with pals could prove fatal. But a routine test to check her sister Kacey, eight, didn't suffer from the same rare disease revealed she was perfect bone marrow match. Brave Kacey - who also had to miss parties and playing for fear of bringing back bugs - donated her "magic" to Milly, who perked up within days.