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Have you sat down and talked to Anna about the things that she'll need to do/know to function as an adult?
Have you sat down and talked to Anna about what it was like, having her mother morph into a crazy person over what must have seemed like a day?
Have you sat down and talked with Anna about anything at all, or just blithely assumed that she would remain somehow on the outskirts of your relationship with her father?
Figure out if you are adult enough, loving enough to accept her as she is, while endeavoring to help her grow up and make better decisions.
Based on some of her behaviors (the bloody towel is disturbing, not for the reason you seem to think, but because it seems to represent a break with reality) it could be that Anna has some mental health issues of her own. Are you ready to be the stepmother to a mentally ill teenager, young adult, adult?
If the answers to these questions are no, then, please, leave. If the flat where you live is NOT a home for Anna, then you have lied. She and her father are a family. And you have not made it a home.