I don't know Royal's work, but when I read the blurb for The Wine of Violence, it sounded right up my alley. I snapped up the first two books in the series (for a whopping $4 altogether) and can't wait to dig in. The series, which is now up to eight, with a ninth coming in December, "stars" a prioress named Eleanor of Wynethorpe. Here's a link to an interview with Priscilla Royal done for Women on Writing. Here's a link to eleven more books from PPP, all priced at 99 cents.
I suspect the first medieval mystery most people read was either one of the books in Ellis' Peters' Brother Cadfael series or one of Candace Robb's Margaret Kerr or Owen Archer mysteries. (There's actually a Medieval Mysteries site that has lots of lists and an open review policy for writers of medieval mysteries.) A lot of medieval mysteries (and series) feature clever female sleuths who are often nuns or churchwomen, but not always. I'm particularly fond of Peter Tremayne's "Sister Fidelma" series, and Margaret Frazer's Dame Frevisse books. I have not read the most recent book, Winter Heart, which is described as a "tale of frigid winter and icy passion."
Also on my TBR list is the first of the Hawkenlye Mysteries by Alys Clare. "Alys Clare" is such a beautiful name I was disappointed to find out it's a pseudonym. The sleuths are Abbess Helevise and the knight Josse d'Aquin (friend to King Richard the Lionheart). I'll start with Fortune Like the Moon, which is available used for a penny on Amazon.