I do not think she has the intelligence to be an Empress. I am not saying she's dumb but the cunning??? naah, they'll eat her alive.
She does not have the lineage hence she has to lean on the ML for every support. She's going to be so dependent and for someone who has lived her WHOLE LIFE in the war zone, it's going to affect her in the long run.
The duties of an Empress are not one to scoff at. If she delegates it too much, she's going to lose respect.
She's one-dimensional, pure even and that's great but for an Empress, I do not think so.
Now if she were the head of his Army, surely she would thrive
BUT
As seeing this is a romance manhwa, they'll probably end up together as that one awkward couple we know...