One of the most important and beautiful themes in "Anne with an e" is that people are capable of changing for the better - at any age. And so we have Mirella, a confirmed and elderly spinster with quite conservative and even rigid views on certain aspects of sodciety. Amd then Anne arrives! She is of course the supreme catalyst for change, and when her lies about going to school are found out the Minister is invited to do some moral exorcism and get her back to school. BUT, contrary to Marilla's expectations, his main advice is that Anne should indeed no longer bother with education and go to school but stay at home and train to be a good wife - which of course was the principal duty and fate for most girls of the time. Prissy and Diana will later be other examples of the rebelion against the norms launched principally by Anne. (But interestingly, very well supported in his laid-back way by Matthew: "I reckon every new idea was modern once - until it wasn't.")

Mirella really can't see that this wife-training thing is the best option for her bright young spark, but is not used to rebelling against the Minister - hence her tortured reflections! She has suddenly realised that thuogh not exactly as a wife she herself has " baked, cleaned, mended and fetched" as she later says for her brother, a self-revelation which turns her almost overnight into a feminist!
This beautiful scene is hugely symbolic of much of the message of the series, and shows how Mirella is already beginning even at her age to CHANGE.