Left: DCE transfer function, centred at 162 light days based on the mean emissivity radius of the CIV BLR, is significantly broader than the accretion disc transfer function at 5315 Å shown in the inset. Its pronounced double-peaked structure is expected from a disc-like BLR geometry (i = 40°), resulting in longer and more complex light-travel delays than in the compact inner accretion disc region. Right: Observed light curve at 5315 Å (green points) compared to various models. The pure accretion disc model (i = 0°; blue) reproduces variability consistent with the expected broadening from the disc transfer function alone. Introducing a moderate 3.9% DCE contribution (magenta) slightly smooths the variability amplitude. Increasing the DCE fraction to 50% (orange) or 100% (red) overly smooths the light curve, failing to replicate its sharp variability features; see Appendix C for details.