Nuns take Vows, Priests receive Holy Orders. They incorrectly mentioned the Nun taking Holy Order three times.
The name on the sleeping medication label was listed as "Sister Theresa". It was specified earlier in the episode that she had yet to take her vows, so she was not yet a "sister".
The Mother Superior's statement in the Confessional would never be stated by any Catholic with minimal knowledge of the Catholic Faith; specifically that she wanted to confess something without specifying the sin in detail.
The Count of Monte Cristo is 464,234 words long. Poole printed out the book, single-sided, on less than a ream of paper.
Sister Marguerite, one of the nuns, clearly wears make-up throughout, which would be forbidden to nuns. Her lipstick and mascara are particularly noticeable when Dwayne is mending the puncture on her bicycle. It cannot be explained by her being a postulant, unlike Therese, as she has been a nun in that convent for several years.