Hey karter,
It depends on what you want. If you "did the deed" and want to let her off the hook, send them their f'ing letter. If she is a bitch and you want to fuck her over for eternity, don't.
Do you give a shit about being shunned? Don't do it. If you could care less, give her what she wants.
It really doesn't matter to you now, go with your gut. Just give them a signed letter if you choose to, and tell them to F off if they want to meet you.
JK