If you really want it over you can.

Tell her it's over.
That you want to be with your wife.
Admit you hurt her. Apologize.
Block her number and email addy.
Delete her emails or designate to spam folder
Delete the email account you used to communicate with her
If your wife is not aware of of your infidelity, TELL her.
Go to counseling with your wife and be transparent.

Be prepared for your wife to be angry and...in the same manner that you took time to develop this other relationship, your wife is going to need time after learning of the betrayal. It's gonna take time to reconcile who she used to think you were vs who you really are. Apologize and if you feel you've apologized too much, apologize one more time. With your actions, not just words. And by all accounts do NOT blame the other woman! You engaged in the affair, you re-engaged after breaking off.

If you cannot stay away from her, do both women a favor and be with the other woman. You won't be the first to divorce his wife. Keep in mind that a relationship founded on dishonesty has a very high failure rate.

I sympathize with you for I can relate. I don't know about you but in my experience bipolar mania can make new relationships alluring and intense. Thankfully and hopefully, the low will come and with it the intensity will get less. Good luck.