You can still have chemistry on screen without getting on with the person. But it just makes your job a lot easier if you don't have to gird your loins, if that's not quite the right phrase, every time you're going to do a scene with that person.
“An inexhaustible good nature is one of the most precious gifts of heaven, spreading itself like oil over the troubled sea of thought, and keeping the mind smooth and equable in the roughest weather.”