I had a similar story... when my mother died and my youngest sister was just 10.. I raised her.. until I left to get married by which time my father had married again anyway.. my sister came to visit several times, and then   3 years after I got married, she came and asked to stay overnight.. when I got up in the morning, she was gone, and so was every item of my clothing, including coats and shoes.. she'd disappeared, completely with everything..  I had to hunt her down through her friends.. and when  I  met her at her work to collect my things,  which she'd bundled into a trash bag.. and asked why she did it.. I got no reply.. .. 3 years after that she broke into my rear garden and stole the bike which had the babyseat on  for my little girl... 
