Is there a difference? What is it?
To me it’s fairly simple. Its fantasy when both (all?) those involved know its fantasy. It’s lying when they don’t.
To complicate it a little I think there has to be intent for it to be lying. One intentionally misleading the other(s).
There is room for one to believe its fantasy and the other to believe they were lied to.
That’s what threads on boards are for
A fantasy is a situation in which I know in advance it is not a faithful representation of reality, and I willfully suspend disbelief -- usually for purposes of enjoyment. A movie or play would be a good example.
A lie is a situation where someone is deliberately misrepresenting the facts of reality to me in order to induce me to maintain a course of action or take a course of action that I otherwise would not, if I knew the truth.
I deliberately leave out of these definitions a great deal because there are issues of value hierarchy. If I lie to a terrorist to save a life; I am STILL a liar -- but it was still better than telling the truth.
I look at a fantasy as the idea of never reaching what you desire be it body, heart, mind, etc... Fantasy rarely come to pass. However a lie is lifestyle...way of life for one who chooses to misrepresent the truth. So a fantasy really is a lie in itself because it will not happen. I fantasize about being with Mariah Carey but I am lying to myself and know it will never be.
Hobbying to fulfill your sexual desires is fantasy.
Denying you hobby to your SO is a lie.
Of course there’s a difference. I’d rather be the object of someone’s fantasy than the receiving end of one of their lies.