Someone Else's Life by Katie Dale

When seventeen-year-old Rosie’s mother, Trudie, dies from Huntington’s Disease, her pain is intensified by the knowledge that she has a fifty-per-cent chance of inheriting the crippling disease herself. Only when she tells her mum’s best friend, ‘Aunt Sarah’ that she is going to test for the disease does Sarah, a midwife, reveal that Trudie was not her biological mother after all... Devastated, Rosie decides to trace her real mother, hitching along on her ex-boyfriend’s GAP year to follow her to Los Angeles. But all does not go to plan, and as Rosie discovers yet more of her family's deeply-buried secrets and lies, she is left with an agonising decision of her own - one which will be the most heart-breaking and far-reaching of all...