not being sure when the series takes place it wouldnt be unusual for girls to board at a convent to be educated
It is own fantasy world since there are plenty of things that does not relate to real life timeline. And that is good since real life monasteries often were not happy places nor would be even close in modern time.
I get this feeling that the old abbess made her feel like this is her second home since it looks like her old man is a worrywart.
Man this takes me back to that day in the Jesuit university where an abbess reamed me for 'not taking good care of my ears' as I was walking to class with headphones on.