Why does "pretend" upset you so much that you are in knots and going crazy? My son thought he was a dinosaur. My stepdaughter thought she was a teacher. My other stepdaughter said her last name was something totally different. I had an invisible friend.
I think you are giving this way too much oxygen, and that attention is keeping this phase going. She probably hears people around her talking about who they love, so she aspires to it. Leave it alone, give it a quick "that's nice" and move on. If you have to discuss it, instead of telling her she can't love anyone, ask her why she loves him. Gently, very gently, help her value people's attributes instead of physical characteristics. Don't criticize her - just say you love Person X or Person Y because they are kind, or always helping out someone less fortunate. But don't critique her and don't do this until you can calm down.
I think you're overdoing this - and your tension is giving this phase a life of its own.