Miconazole is pretty benign. Sort of like Corid. In either case, it's harmless to do the treatment even if you're uncertain what you're treating. If anything, it will rule out sour crop if it fails to work. Then we go on to the next treatment for impacted crop.
It does sound like she has sour crop. As @Wyorp Rock suggested, begin with the vaginal cream. I just buy the seven day cream and don't mess with the suppositories. I take the tube, pry open the beak and squirt a bunch into the mouth, sort of like squirting whipped cream into your mouth. Yum! The...