Let it go unless she reaches out to you again. Also, don't refer anymore jobs to her.
Dear Prudence,
In 2019 I left my job of several years for a position at a more prestigious company. I’d become very close friends with a coworker there, “Jessica,” who’d started just a few months after I did. We both hoped to move to the company I work for now. She was supportive and encouraging when I got my offer. After a few months, another position opened up here, and I encouraged her to apply. When she came into the office for interviews, I mentioned my excitement to “Amanda,” who had also worked with us at our old company. She was shocked and told me Jessica had always been deeply competitive toward me and had often tried to undermine me secretly. In fact, Jessica had spoken to our supervisor more than once (unsuccessfully) asking to be promoted into a position above me. I had no idea Jessica felt this way! I had thought it was a little odd when Jessica took over my office the day after I left, but I didn’t worry about it (it did have a great view). Later, I spoke to other coworkers we had in common, and they confirmed what Amanda told me. Now I realize I was being played: Jessica acted like a close friend to gain an advantage over me, but didn’t actually care about me the way I cared about her. I feel like an idiot, not to mention sad over losing a friend. I’m also embarrassed over sharing details of my personal life with her.
Fortunately, Jessica did not get the job at my new company, but ever since her interview she has been distant, and we’ve stopped communicating as much. Should I tell Jessica directly what Amanda shared with me and try to discuss the situation? Is it worth even trying to salvage the friendship? How do I avoid falling into a trap like this again?
—Bestie Betrayal
Re: Let it go unless she reaches out to you again. Also, don't refer anymore jobs to her.
There is no value to confronting her. She'll just deny it. Depending on your location and industry it is possible that you'll have a future professional experience with Jessica. If that happens, it will serve you to know who she is without her knowing that you know.
Backstabber is pedaling back from the friendship, because the LW has outlived their usefulness. Good riddance. At least the LW knows why and it's that much easier for them to let this toxic friendship fade away.
Confronting her would do no good. LW wouldn't get any satisfaction and probably end up having more questions and more hurt. Plus, since it sounds like they will cross paths again eventually, it's best to maintain professional politeness. But LW now knows the truth. And you never know when that will come in handy.