to be a little pedantic, if you take in account the rate of expansion of the universe, and take as a truth that the ghost stays stationary in spacetime, earth would disappear in an instant
That's a fair point. So then one might expect the ghost to continue their motion tangential to the orbit of the earth, and so they'll float away.
However, the theory of general relativity suggests that gravity isn't really like other forces. It doesn't push or pull anything at all; but rather its bends the fabric of time and space. Objects 'falling' due to gravity, or 'in orbit' around a planet are actually moving in a direct straight line in curved space-time. And this is why gravity still applies to massless objects such as light. So then, I'd say the ghost would still be affected by gravity - and that their main concern would be falling into the earth rather than drifting away.
Would that not depend on your inertial frame? Like isn't the entire concept of being stationary relative to spacetime not an actual thing? I'm not trying to be pedantic, BTW, I literally don't know the answer to my question.
Yup. Same as the time travel meme that was on the front page recently, this relies on there being a fixed inertial frame which is not a thing in our weird universe.