The thermal velocity of the electrons will be fast due to their high temperature and low mass:
The net result is that both ions and electrons stream outward at the speed of sound,
In astrophysics, "ambipolar diffusion" refers specifically to the decoupling of neutral particles from plasma, for example in the initial stage of star formation.
The neutral particles in this case are mostly hydrogen molecules in a cloud that would undergo gravitational collapse if they were not collisionally coupled to the plasma.
The plasma is composed of ions (mostly protons) and electrons, which are tied to the interstellar magnetic field and therefore resist collapse.
In a molecular cloud where the fractional ionization is very low (one part per million or less), neutral particles only rarely encounter charged particles, and so are not entirely hindered in their collapse (note that now is dynamical collapse, not free fall) into a star.
[2]: 285 In the case of ionic crystals, the fluxes of the diffusing species are also coupled due to the electroneutrality[3]