Wouldn't all that matters here be their relative velocities to Andromeda, and not to each other? And relative to Andromeda, the person in the car might actually

Wouldn't all that matters here be their relative velocities to Andromeda, and not to each other? And relative to Andromeda, the person in the car might actually be going slower. Separately, I don't think chronology is broken. It's ok that there is predestination because there is no way for actions taken here to propagate back there in time to change things. If a change does somehow propagate back through a wormhole or something, it's all good, just spinning up another dimension probably...