  The recent Gamma-Ray Burst (GRB) GRB 211211A provides the earliest ($\sim 5$
h) data of a kilonova (KN) event, displaying bright ($\sim10^{42}$ erg
s$^{-1}$) and blue early emission. Previously, this KN has been explained using
simplistic multi-component fitting methods. Here, in order to understand the
physical origin of the KN emission in GRB 211211A, we employ an analytic
multi-zone model for r-process powered KN. We find that r-process powered KN
models alone cannot explain the fast temporal evolution and the spectral energy
distribution (SED) of the observed emission. Specifically, i) r-process models
require high ejecta mass to match early luminosity, which overpredicts
late-time emission, while ii) red KN models that reproduce late emission
underpredict early luminosity. We propose an alternative scenario involving
early contributions from the GRB central engine via a late low-power jet,
consistent with plateau emission in short GRBs and GeV emission detected by
Fermi-LAT at $\sim10^4$ s after GRB 211211A. Such late central engine activity,
with an energy budget of $\sim \text{a few }\%$ of that of the prompt jet,
combined with a single red-KN ejecta component, can naturally explain the light
curve and SED of the observed emission; with the late-jet -- ejecta interaction
reproducing the early blue emission and r-process heating reproducing the late
red emission. This supports claims that late low-power engine activity after
prompt emission may be common. We encourage very early follow-up observations
of future nearby GRBs, and compact binary merger events, to reveal more about
the central engine of GRBs and r-process events.
