Kudos to user14111 for providing the key to cracking this problem by directing me to the Mathematical Fiction site. The various search terms I tried did not give anything useful so eventually I resolved to "Browse by Motif", choosing the motif "Female Mathematicians". There are only 256 entries, and after browsing the first few pages I found what I was looking for: Distances by Vandana Singh.
Most members of Anasunya's species have "a gift". Since she has a gift
of mathematics, she leaves her aquatic home and begins working at the
Temple of Mathematical Arts. She has a gift that allows her to
intuitively understand, almost to live in equations and is asked by
another alien species to study equations describing an intricate
higher dimensional geometric object that is beyond their
understanding. As she studies it, she comes to think that the
embedded, self-intersecting, 4-dimensional sub-manifold may not be
merely interesting and beautiful in an abstract sense, but may have
tremendous significance in the real world as well.
hits the main point, a female mathematician who "lives" mathematics, but does not mention some of the other points I remembered (the desert world and the application of the equations to FTL travel), which is probably why my searches failed. Other reviews on Goodreads confirm these points though, and in particular the review here confirms that the other race are from a planet called Tirana:
when mathematicians from the planet Tirana, 18-light-years-distant,
ask Anasuya's help in solving a series of equations, she finds the new
geometrical space they present her with intriguing. But as she
explores the new space, she soon comes to suspect that it represents
an actual physical system, and that the equations she is being asked
to solve have a significance the Tiranis are concealing.
The point is that the equations could lead to FTL travel. The Tiranans want the solutions, but don't want to reveal why, so that they can keep the secret of FTL travel to themselves.