Why didn't christiane's mother take her to rehab?

In the book, rehabilitation centres were too expensive for her mother. Therapy centres had extremely long waiting lists and you had to have been clean for months for them to even consider you. At one point, later in the book, after she is arrested her mother took out a loan to get her put in rehab. However, it just turns out to be a Scientology sect where they do little to rehabilitate addicts, they really just want their money. Christiane ran away from there. Then she checks herself into a mental institution but manages to run away from there aswell by getting herself admitted to hospital. She managed to successfully withdrawal a few times but would always fall back into Heroin within a couple of weeks. Almost always the relapses would centre around Detlef in some way.

In the book there are a few passages written by her mother. Basically, her father had been very protective of her throughout her life and she wanted to give Christiane the freedom she never had as a child. Her mother did a lot to try and help her but she found it very hard to get her a placement anywhere in Berlin. So in the end she sends her to live with some relatives, where she does end up getting clean.

You can find the movie on youtube and I would definitely recommend the book, it was really good.