'Sorry, but as you said those years ago "we're moving in different directions". I'd like to think I'm fairly successful now, and you showed me who you were at that time. To quote that infamous quote, "If you can't handle me at my worst, you don't deserve me at my best". If I didn't have the money I do now, we both know that you wouldn't be here.

There isn't any chance for there to be an "Us" again, because I don't feel anything at all for you now. Now, if you'll excuse me. I have a date with a wonderful woman, and can't afford to be late due to texting you.'

I get you don't want to be petty, but this right here would work fine to fully get her off your back.

If you just want to be straightforward, just say "I appreciate the interest you've shown in me now. That being said, I no longer desire a relationship with you, and do not feel the way I used to feel for you. You made your decision back then, and we have since become different people. I wish you well in your future, but we are moving different directions from one another at this point in our lives. Maybe if we hadn't split back then things would be different, but now too much has changed." Say you goodbyes at your discretion.