What would be the best way to politely decline a persistent Jehovah's Witness at your door?

I was in med school when a JW lady knocked on my door. She said she had a book from her order and said it cost a quarter. I asked her: “Is your religion for sale?”, to which she was taken aback: “Oh, no!”, she said.

She shared some stuff while holding onto a Bible. I asked if she believed in the Bible and she said, “Oh, yes!”.I then said: “Some other religious folks had come by, and brought this”, I produced a Four Spiritual Laws booklet. I asked about John 3:16 in the book: “Is this in the Bible?”.She turned to it. There it was: “For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life”. I asked: “Is this true?”, “Oh no!”, she exclaimed. What about this: “All have sinned and fall short of the glory of God” (Romans 3:23). There it was in the Bible. Is this true? “Oh no!” she again said. “God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us” (Romans 5:8). Again it was in her Bible but again, “Oh, no!”.

I just finally said: “Can you find out for me what’s actually wrong with these statements and you get back with me?” She said: “Yes“ in a relieved fashion.

I watched her leave the two-story apartment building and walk across the street where two other “witnesses” were. They all looked at the Gospel tract I had given her and she pointed at my apartment as they all looked. I'm behind the curtain: “Oh, no!”.

I’m not the guy behind the curtain above,  just a “witness” to the one who is (and whoever shall be).