It depends on what you're used to. When I lived with my parents, fights were screaming and shouting, with doors slamming. My partner doesn't handle conflict that way and early on in our relationship I would have said we never fought because our disagreements never reached the level that I considered a fight.
If Jinger is used to fights that involve screaming, but she and Jeremy fight without raising voices, she may categorize those fights as disagreements. If they have had disagreements, of any level, and have learned to resolve them, then I consider that a sign of a healthy relationship. I'm not concerned about a lack of fighting.