As ghosts would signify some kind of spirituality and afterlife, why do you not then believe in God ?
I don’t see why the existance of ghosts would require an afterlife, or a God. Ghosts aren’t a part of Abrahamic religions as far as I know, which is why my gf thinks it’s a demon.
A ghost whilst not evidence of a creator points at least to life after death.
The only ghost I can verify the existance of is that of my sister. She was my identical twin, so my hypotheis is that if a ghost is some kind of manifestation of a spirit or soul then the division of a zygote two create identical humans would also necessarily require the spirit to also be divided. From this my assumption is that whatever happens to a spirit after death cannot be completed yet for her as part of her (our?) spirit is still locked inside of me.
I don’t have any empirical evidence for this, but it seems to be logically consistent with what I have experienced.