You must.

To this one person I used to know.

I hope you did not do to her what you did to me because she did not deserve that.

(I did not deserve that either.)

Or if she did, at least let her know what went wrong.

Allow her the closure she deserves.

Even if she does not accept it at the moment, it will help in future.
I did not get the closure I badly needed.
Till now, I didn't get it.
But I managed to close the book anyway and found new things that made me happy.
But that doesn't mean you can keep getting away with doing it to others.

You cannot do this anymore.

You cannot do this to anyone.

You cannot leave someone hanging.

Especially after all those words and promises you made.

Words don't mean anything if your actions prove otherwise.

I spent quite some time wondering what went wrong, how I could've/should've been better, everything..

I'm over everything now and I've let whatever you did pass.

I'm happy now with someone else.

I'm just saying..

You must stop doing this to anyone.

You must.