Thank you for reaching out to Wefugees again and sorry for the waiting time!
Has your sister already notified the Berufsschule/ her Ausbilder*in about her pregnancy in general?
As I've read on the following website, you can notify your Berufsschule about the pregnancy (and estimated date of birth) in written form. They may ask for a medical report stating you are pregnant, but when you hand it in, you can always remind them that they are bound to discretion - hence, not allowed to tell anyone.
Why it's helpful to tell them: In Germany, you will receive so-called "Mutterschutz" (Maternity Protection). According to the law/ Mutterschutzgesetz and other regulations/ Mutterschutzbestimmungen, you are entitled to a special occupational safety and dismissal protection, which also forbid certain kinds of activities at work to keep you safe.
Furthermore: you do not have to be afraid of facing the termination of your job/ Ausbildung. On the contrary, from the beginning of your pregnancy up until the fourth month after the birth of your child, you receive the previously mentioned dismissal protection (meaning you can't be fired), even in your probation period. The prerequisite is that your employer knows about your pregnancy.
Source (in German, please use a translation program): http://www.azuro-muenchen.de/hilfe-ich-bin/schwanger-in-der-ausbildung.html#chef
And another helpful source: https://www.schwanger-unter-20.de/schule-ausbildung-und-job/ausbildung-und-job/#c4438
There are several support options for mothers in Germany, also financial support for parents/ child benefits. You can have a look at these following websites for a more detailed overview:
If your sister would feel better to speak to someone in person about the pregnancy, her Ausbildung and the future, there are local pregnancy advice centers that she can reach out to.
Here is a telephone number for pregnant women in distress (you can remain anonymous, if you wish)/ "Hilfetelefon für Schwangere in Not": https://www.bafza.de/aufgaben/hilfetelefon-schwangere-in-not.html
This BAMF article on pregnancy can also be helpful regarding where you can find support: http://www.bamf.de/EN/Willkommen/KinderFamilie/Mutterschutz/mutterschutz-node.html
I hope that these sources and contact details help your sister to find the support she needs! Feel free to reach out to us again if you need any further assistance or are unsure about anything.
All the best to both of you,