<human>: The main problem is that she is my ex-girlfriend's best friend.

A few months ago my girlfriend [23 F] of two years broke up with me.  During the relationship, her best friend and I became very close friends. We were always flirting with each other in jest, even in front of my girlfriend. It was never a problem, and there was never even a hint of cheating. After the breakup we continued being close friends.

One month after my breakup, my close friend and I were drunk and alone together, and we started messing around in bed. We decided it was a drunken mistake, and wouldn't happen again. After this, and a couple more weeks of heavy flirting, we slept together, fully sober. We both said we didn't regret it, but we didn't discuss it further.

Over the next few weeks she stopped texting me all the time. She cancelled plans one weekend at the last minute, and has been unresponsive ever since. Now we've gone a couple of weeks without talking at all (it used to be rare to go more than a day without talking).

I don't want to lose her friendship, and I regret letting things escalate between us. I also don't want to ruin her friendship with my ex-girlfriend.

From an outside perspective, does it seem like there's a way for me to repair this without anyone getting hurt? Or is it over for good? I would love to start dating her, but it seems out of the question, and I would be more than willing to forgo that just to have her back as a friend.

Thanks for any and all suggestions.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: Slept with a close friend, who happens to be my ex-girlfriend's best friend. How do I go about saving the friendship? Or is it over for good?