Show of Hands

End it quickly and run the other way.

this happened to me. I ended the friendship

I think how long you have been in the happy relationship and how committed you are to it is definitely a factor, but assuming that you don't want that relationship to end, you've got to try to curtail the intimacy with the new friendship.

Straight answer: happy fulfilled relationships rarely tolerate open sexual license. I'd politely and carefully cut off any hints of intimacy. I would include occasional comments of how sexually satisfied I was and what a wonderful lover I had. Maybe even toss in a few whoppers. Like you can't believe what we did last night. OMG it went on for hours.

I'd discuss it.

I'd end the friendship. There is no way I'm doing anything to spoil the loving relationship that I already have. And, especially if the new intimacy is uncomfortable. I don't owe anybody anything when it comes to something like this except for my current partner...I owe him 100% love, trust, and faithfulness.

Talk about it. Maybe it's time to end the first relationship.