Grown-up in a Kid's Body

My 11-year old niece has had a very tough life. Her mom is an alcoholic and drug addict and her dad (my younger brother) has never known what it means to step up, be a man, and take care of his child. Because of her tough life, she's had to grow up very fast. Having a conversation with her is like having a conversation with an adult, most of the time. Because of that fact, it's easy to forget that she's only 11. Although she understands a lot of the inner workings of adult life and can converse about them intelligently, she is still just a child who often still does childlike things. One of the things that her mother taught her was to be deceptive and keep things from people. Because of some things that have happened, she now lives with my parents and has attempted to keep things from my mom. Of course all kids lie, but it's never good to hide things. My mother is 61 and has been taking care of children since she was 8 (she's one of 12 children). So she's pretty much seen it all and knows every trick in the book. My niece is a good kid who's very smart, but I just hope that she doesn't let the wrong stuff she learned during the first part of her life hamper her from growing up to be a good adult. I'm trying my best to make sure that she doesn't end up another statistic.