I teach psychology to undergraduate students while I am studying in my PhD. The module's assignment is a research report on a subject of the students' choice (the report has to be written in English). Before the data collection the students had to send me their research proposal and their ethics form for approval. I have given approval to all the students and they have already started to collect their data.
However, yesterday I was searching some studies about my PhD and Ι found out that a student had copied and pasted whole parts of a Greek thesis in her research proposal (actually she has "stolen" the subject and research questions as well as many parts of the introduction) and translated them verbatim in English.
I am very confused on what to do. I am pretty sure that her report will constitute a complete copy of the other students' thesis. However, due to the fact that the text will be translated, the Turnitin score will possibly come out low. Should I inform the university's principal or wait to see what will happen?
Update: Thank you all for your answers. You helped me a lot! Just to explain why I asked about how to deal with plagiarism: I am quite new in this job (lecturing)and additionally the college I am working for belongs to the private sector in Greece (i.e. students pay to study in the specific college smth that is not the prevailing way of studying here. All the universities are free of charge). So far, I have noticed (due to my experience as a second marker) that there is a silent policy of not failing students unless they are completely incompetent to study in the college. As you can understand, the students' level is quite low. So, I am afraid that if I report a translated plagiarism (smth that cannot be indicated by turnitin score meaning that I deliberately searched for it) I will "accused" of discrimination towards the student. Additionally, despite their low level the students (as well as their parents who pay for their studies) react aggressively when they receive a low grade. So, I am afraid that I will have to deal with this, too. That is why I am very concerned about what to do.