Final answer:
Veronika should click the zigzag icon in the toolbar of the Timeline panel to toggle the Graph Editor and view her animation as a graph with keyframes.
Step-by-step explanation:
To view the animation of the box fan blades as a graph with the keyframes using Linear Interpolation mode, Veronika needs to access the Graph Editor in the Timeline panel. She should click on the icon that resembles zigzag lines in the toolbar at the header of the Timeline panel. This icon toggles the Graph Editor, allowing her to view and edit the interpolation of keyframes in a graphical representation.