The schools (ammattikoulu) explain (or should) all the workplace regulations and legislation. It is part of the curriculum.
Shifts in the restaurant sector are based on periods of three weeks. You are given your shifts at the beginning of the period for the following three weeks. The number of hours worked per week is an average over the three-week schedule. It is not calculated on a weekly basis.
Yes, the attitude towards work placement apprentices in the restaurant business sucks. (The working conditions in the sector are dreadful, even when you are being paid for it.) My son regularly works 15-hour shifts back-to-back with NO breaks for meals. The companies are too mean to pay for cleaning staff for the kitchens so they are expected to clean up themselves AFTER their shifts for which they do not receive payment.
But if that is the sector she is going to work in, she will probably have to get used to this kind of thing. In this case, work placement, I guess it is the school that needs to have a discussion with the employer. The employer is being CHEAP because if they use agency staff (Staffpoint) during a bank holiday weekend, it costs them double.
There are some buses from Olari during the weekend and I guess there is also Uber for a cheaper taxi ride. Or maybe she could find somebody else at work who will share. Or go sick - but they really won't like that.