Can my teacher give me a 6 for plagiarism?

Hey,

you have obviously already read you into an answer from me with similar content 😉

I would recommend asking the teacher to explain what he is convinced that it is plagiarism. He's got to fix it to something. The abdominal feeling alone wouldn't be enough in my eyes. In any case, not for a 6, because even if, in all its searches and the preparation of the presentation content, it should not only have used Google and secondary literature, but (purely hypothetical) should also have used ChatGPT for an explanation/disclosure of any facts, then at least the performance of the lecture appeared, the question whether it is content/fold correct, whether it was complete or whether it was essential, etc. All of this would have to flow into the note.

Yes, plagiarism/description is sometimes difficult to prove and also the reasoned suspicion is theoretically entitled to draw consequences.
Example: in a class work some pupils have recently written off by a good fellow student. This was not noticed during the work, but at the correction it was noticed that everyone sitting around him have solved the task exactly the same. Includes the computational error that the central student has made and some have “worn off”. Thus, in one line a zero was a zero, in the next line a 6 and later a zero again. There, the one from which it was written, probably had an undeniable handwriting and the descriptors could not distinguish the zero from the 6. Here was very clearly written off, but it could not be proven 100%. The students concerned got the chance to reckon the task again and explain what they did and oh miracles, only one could explain what he did. The others don't.
These pupils did not evaluate the tasks, but only those who were not (so obviously) written off, which naturally led to poorer grades.

So you see, teachers have a certain scope for action and they are not stupid and have experience. Such a feeling is often not about.
However, teachers – like all people – can make mistakes and mistakes themselves.

In this case, I would therefore seek the conversation with the teacher, to tell him how the preparation was going, what sources were used, to ask him to justify his suspicion and, if necessary, also to get the school board. For the teacher should also be concerned that his obviously very controversial decision is taken by the school management. For short or long, he'll probably get back from the head of the school. So that could also initiate your girlfriend. This also has a more stable effect.

By the way, the 1:1 write off from books would also be a kind of copying and, if it appears, could lead to a minor note.

I'm curious how it works! I'll push her thumbs when your girlfriend deserves it! 😉