what wud they do? its the first time this has happened
They will probably just give a mark of zero for the work and possibly a warning but, really, it's up to the institution themself.
But if its a first time and if shes in first year they would be more lenient. Probably at worst just get a 0 for that essay. First year is the best time to make these kind of mistakes. If she isn't completely sure as to how she plagiarised make sure she asks her lecturer to explain, especially since its the most annoying way to lose marks if you didn't do it intentionally. In my experience lecturers are more than happy to explain things like that.