I dont thik you notice what Im referring to, so I will load an image with some text and indicators.
In the interim, its quite a decent shot, V1 for a start.
To get terminology right, you have a main light source, normally situated to the side of the subject 45 degrees horizontally, and raised to "look down" about 45 degrees; then the light at the camera position, is called the "fill light" and is normally at approx 1/3 less to 2/3 less power.
The settings you use for the camera would normally be the flash synch speed, and you adjust exposure by either/or/or both the light power and the aperture.
Use a single focus point with the 6D, not multiple points. It looks like youve focused very slightly in front (closer to the camera) that her near eye, - just a little.
So im not certain if this is the want you se the lighting up. It look right when you have a shadow by the side of her nose, thats tilted down towards her jawline, as a very rough guide.
What I see if too much light behind on the background. Otherwise needs some contrast, and dropping the light on the background resolves the contrast problem.
Im uploading a few mods, - 1 is the original shot adjusted as mentioned, with the eyes a little sharper, and the background/contrast adjusted; 2 is a softened version. Both are cropped to A4 place her eye on a third.
Next uploads will be one to indicate those odd areas, - I cant do anything about them (I need your input) and I will look also at the mono which appeared as I was typing.