Welcome back to the Wefugees Community and thank you for reaching out to us again.
First of all, I am sorry to hear that your sister's appeal got rejected by the court. In theory, it is possible to apply for a so-called "Berufung" - to re-appeal. This application needs to be submitted by a lawyer at the same court within one month after the rejection. In case the application gets accepted, the case will be subsequently ruled at a higher court (Oberverwaltungsgericht). However, the second appeal is only in very exceptional cases a promising option. Whether there is a realistic chance through another appeal should carefully be discussed with a specialized lawyer. We looked at a similar situation here before and you may also check out this thread for more information.
Whether your sister is at risk to get deported is hardly possible to assess without knowing her situation in detail. I explained the general legal requirements here a few days ago.
I would highly recommend her to get individual support in a migration counselling office. In this specialized service, counsellors will look at her situation in a holistic way (incl. her personal conditions, skills etc.) and explain all options she may have now (as securing her stay through vocational training, work, family etc.).
Please let us know if you need help in finding a respective office close to her location - we are happy to make some research.
In any case, also don't hesitate to get back to us with any further questions.
All the best,