We study the real-time dynamics of electron coherence in a double-quantum-dot two-terminal Aharonov-Bohm geometry, taking into account repulsion effects between the dots’ electrons. The system is simulated by extending a numerically exact path-integral method, suitable for treating transport and dissipation in biased impurity models [D. Segal, A. J. Millis, and D. R. Reichman, Phys. Rev. B 82, 205323 (2010)]. Numerical simulations at finite interaction strength are supported by master equation calculations in two other limits: assuming noninteracting electrons, and working in the Coulomb blockade regime. Focusing on the intrinsic coherence dynamics between the double-dot states, we find that its temporal characteristics are preserved under weak-to-intermediate interdot Coulomb interaction. In contrast, in the Coulomb blockade limit, a master equation calculation predicts coherence dynamics and a steady-state value which notably deviates from the finite-interaction case.