Dear Amy: My best friend of many years, “Alexis,” dated married guys for years of her young adult life, basically pulverizing several marriages. This behavior continued during the early years of her own marriage.

Our group of girlfriends have tried to “right her ship” throughout these years.

Last week I learned during a group dinner that Alexis had an affair with my former boyfriend “Sam” during the time he and I were together.

Sam and I shared a significant, long-term relationship.

It sounds like their affair lasted for several months.

During my dating years with Sam, Alexis constantly pressured me to drop him. At the time I didn’t know why, but now I wonder if she had an agenda.

To be honest – I am less mad at him, and absolutely furious with Alexis. This feels traitorous. After I asked her to detail this affair, she admitted to it, and also downplayed it. She then attempted to gaslight me by saying that I was jealous and overreacting.

My biggest take-away: I watched her wreck other marriages, but somehow never thought she would harm ME.

If Alexis had admitted to this, apologized and asked for forgiveness, I’d definitely get there, but she says she has nothing to apologize for, is being flippant with me, and is telling others in our social group that I must be a nutcase, because this was YEARS ago and thus too infantile to discuss.

Yes, I am angry, and this is NEW information for me!

I loved the guy, and Alexis KNEW it!

Where do I go from here?

– Betrayed

Dear Betrayed: From here, you should go to your room, your car, your treadmill, your coffee shop – or any place where you go to lick your wounds, ponder the events of your life, and attempt to make sense of things.

Yes, this is brand-new information for you, and your reaction to this revelation seems completely rational.

You’ve also identified your own hubris in believing that this best friend would carom her way through other relationships and marriages like the giant boulder in “Raiders of the Lost Ark,” while also believing that you, like Indiana Jones, could somehow successfully outrun her.

Yes – best friends trust one another. This trust basically defines the sort of intimate friendship you and Alexis have shared.

I’d characterize her friendship style as scorched earth.

In my opinion, no one gets to brand an upset and struggling person as a “nutcase” without consequences.

Once you clarify your own feelings, you’ll decide what those consequences will be.

You can email Amy Dickinson at [email protected] or send a letter to Ask Amy, P.O. Box 194, Freeville, NY 13068.