Could she have? I think so. It appears that she had little to no oversight and her superiors gave her no checks and balances or anyone to monitor what she was doing. The fact that the entire power at the school rested in the hands of the headmaster shows you just how fragile and poorly designed the school was. Like a dictatorship, the power to do a lot of good was there, but also the power to do a lot of harm.
There is no indication she did sexually abuse the students though. It doesn’t really appear to be in her nature.