Hi, darkness. Sorry, late in the game but I can relate to what happened to you sorta.
I had a girlfriend a long time ago that was actually from church. She's affectionately known as the "girlfriend from hell". I tried to be the best person I could for her and all she did is play mind games on me. To make a long story short, I broke it off and she, like your ex, proceeded to kill me and my reputation at church. I started to get the cold shoulder by many a person who I thought were my friend. This killed me also spiritually as I no longer felt welcome to worship at that church anymore as many people were snubbing me, but it was a church that I grew up in. These people were not only fellow church goers, but also in my close circle of friends as I spent much time doing church related activities. It was a painful time for me.
It was tough but I persevered. Sorry if this has too much religious over tones. For me, I went to church to worship God, and not just to make it a social activity. That's what got me through these tough times. I continued to be friendly despite how I was treated by others.
I said to myself if they were really my friends, they would know who I am, despite the lies that were passed around by some immature girl. That is what I would like for you to take away from this post, darkness. If these poeple were really your friends, they would stick by your side or would approach you about these lies and not just accept them as fact. You don't need people in your life that'll drag you down.
Anyhow's, the happy ending is that I didn't do anything vengeful (although the thoughts did cross my mind). I chose to act like a gentleman and I feel it was the best way to go. Your character will speak louder than the actions of your ex. Go about life as usual. Those people that snubbed me now talk to me as if nothing happened. I feel the truth will eventually be known and will set you free. Just my 2 cents.