Often, trying to pick a specific feature or geometry maybe difficult if many other features are in the same area. This is often the case when trying to select the correct edge for applying a Fillet.
To make things easier, simply use the SELECT OTHER option when you pick or RMB (right mouse button) select the desired geometry (see below).
The SELECT OTHER icon, when pressed, will show all features and geometries in the nearby region. Just scroll and select the geometry you want, and go from there (see below).