What you should first realize is that "God" is not an individual being as mainstream religions believe, but rather a force or energy of which all things in the universe are a part of. So in that sense, all spirits, whether incarnate as a living being or having passed on, are all part of "God", so the answer to your question is both yes and no, depending on how you look at it.

As for what that lady told you, that is absolutely false. Spirits/ghosts are very real, and most aren't "demons" as she believes. People are just naturally afraid of what they don't understand.

Hope this helps.