Maybe Leysritt will school Miyu in the art of Taking it Really Easy but Still Getting the Work Done (with a concentration in laundry). They're her mentor maids after all, even if Sella has been slacking off.

Anime has taught me that if Miyu is too harsh, it really means that she's too kind hearted, bawwwh. Luvia took her in when she had nowhere to go, so she undoubtedly has a tragic past!