Do you have any examples of these "nefarious" things ? I know it's only hypothetical but I'd like to know :)
OK, for instance, do you understand Polish to know what you are signing? You could be placed as the 'representative' of the company, and with it, you could be listed as the one who has decision-making powers in the company. I can't explain this too well as it's a Polish concept, but it's possible that she could take on debts using your identity as the one who made the decision to take on those debts. For instance, let's say she orders something in your name. She doesn't pay for those goods, but when the time comes to pay, it's you that made the order on behalf of the company. That means that you will be held responsible, even though you thought you were only a shareholder and not a decision-maker.
That can then lead to criminal investigations, with your extradition to Poland to answer criminal charges, even for small amounts.
If she is honest, ask her to produce the financial statements from 2016 and 2015. That should be your first clue - if she refuses to produce them, then something is wrong. If you want, I can explain how to check some publicly available records which should give you insight into how the company is operating.
My strong, strong advice is not to get involved. I would be very reluctant to get involved, even as a Polish speaker living in Poland.