So, Marla is from a book series by T. A. Pratt. There are four books out, and the publisher dropped it after low sales, despite the cliffhanger (that incidentally is Marla's reason for being in SLT).
Anyway, the books themselves cost money (that goes to support the author), but they are in paperback -- first one is
Blood Engines*. The author also has free stuff on his site (so you can figure out whether they are worth spending the $7.99** paperbacks cost).
Pale Dog, a short story that is pretty much a simple investigation involving a haunted suit and the eponymous dog.
Bone Shop, a (short) novel that chronicles the time from Marla's arrival in Felport as a teenaged runaway to her election as Head Sorcerer.
T. A. Pratt has also promised a Book 5, entitled
Broken Mirrors, put online for donations (well, free with people encouraged to donate, and later chapters only going up if funds happen). I figure spamming all of you with 'Read This Now' will help give the author money, so he will write more. (It's like a pyramid scheme, except you guys get good urban fantasy with a female protagonist that doesn't turn into romance halfway through.)
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* It's a bit of a rough start, since it doesn't take place in Marla's city, and has some Research Fail. (Seriously, the Aztecs didn't sacrifice nearly as many people as Pratt seems to think they did -- also, why does a Central American sorcerer follow Aztec gods, anyway***? They were farther north than that.)
** Or maybe more, if you live overseas or in Canada, because the publishing industry doesn't love you as much.
*** I can think of some reasons, but they are spoilery.