Scholar of the Crown - The Heirs of Willow North, #3

Veronica North, quiet and shy widow of the King of Tremontane, spends her days drifting from one charitable cause to another. Longing for something different, she returns to the Scholia, foremost educational institution in the country, to complete her education. At fifty, she is by far the oldest student there, but soon makes a place for herself within the community. When a friend and fellow student is murdered, the tragedy draws Veronica into the investigation.
Despite official warnings to leave it alone, Veronica's determination to obtain justice for her friend brings her ever closer to the truth-and leads her to discover a side of herself she never knew existed.