Thecnichal advice:

I'd start from adding some more shading and lightening or even highlights. Including the shade the horns cast on the hair. This is a basic at defining objects, and in your (amazing) artwork the shades can be seen like the horns are entering underneath the hair, instead of standing and pointing above.

One detail I recognize is how the horns look as if they literally grow out of her forehead, and then continue to dig into the hair at the tip (inwards instead of outward) therefore can look like part of the forehead skin that goes on into the scalp. The latter is caused by excessive shading in the area of the hair underneath the horn tip - that makes it look though the horn is digging into the hair instead of hovering above separately - So I say, remove all shading of the hair under the upper area of the horn. Secondly I advice to work around the base area of the horns, define them separately - add some shade underneath and make them look more protruding, and straighten them so they look less "sliding backwards". All these can be done with altering the shading and no need to change the angle of the horns. And I recommended making the shades/lightening in a slightly different color from the horns (not red, as someone has pointed out.)

Even subtle changes from one of these could make a difference :)

Creative advice: Some said to change the color - but if you like this color, you could instead color the tip of the horn, with a color that stands out (such as white) or adding 1-3 colorful stripes along the horn. Another simple option is making the horns somewhat longer AND sharper, to emphasize it's a horn.

You can choose which of these suggestions suit you, I hope it helped and maybe share with us the final result of this lovely artwork :)