Well, you could let your ex know that you never signed a Legal Release Form, and if she distributes or continues playing the recording, you'll have her butt on People's Court before she can say Jerry Springer.
That was mostly a joke, because it wouldn't help the rep much - only give more advertising to the situation.
Regardless of how tacky it is to record someone without their consent or knowledge, anyone listening will consider the source. Who is the more credible, her or you? If anyone is brave enough (or insensitive enough) to ask you about it, just let them know that any actions between the two parties were completely consentual, and leave it at that.
And remember, fish and news go stale after a day. There will be another scandal circulating the hallways before you know it.
Oh, and you might want to consider a bit more discretion (or at least use a bug detector) in future adventures.