Fighting in a dream often externalizes an inner conflict rather than describing an actual grudge -- two parts of yourself in disagreement, dressed up as an opponent you can see and swing at. Who you're fighting, and whether you're winning, usually says more about the tension inside you than about that person at all.
The Sun answers those who are ruled by Mars, and Mars answers those ruled by the Sun. - Picatrix (Andalusia, ~1000.AD)