[4][1] From 1995 until 2006, needing a broader field of vision, she worked at the Glenbow Museum, Calgary as senior art curator and twice interim vice-president (exhibitions and collections).
In 2002, she curated the major travelling exhibition, The Group of Seven in Western Canada, accompanied by the first comprehensive book on the subject which she edited and for which she wrote the introductory essay.
Under her leadership, the gallery earned an unprecedented 20 performance awards between 2013 and 2019 for tourism, partnerships, exhibitions, writing, staff excellence, volunteerism and community recognition.
[7][1] She also has written numerous articles for catalogues such as ones on Frances Loring and Florence Wyle in Uninvited: Canadian Women Artists in the Modern Movement.
[1] In 2017, Mastin volunteered for five years of service on the board of directors of the Ontario Association of Art Galleries including a term as president (2017-2018).
[1] In 2022, she served as an Adjunct Member in the Faculty of Graduate Studies in Art History at York University, Toronto, Canada.