Introduced a girl I was seeing into my friend group, now she's obsessed with one of my friends, and is trying to rip his current relationship apart?

We never officially dated, we got to the point we confessed we had a crush on eachother but it didn't progress further than that. Skip ahead a bit I introduce her to my friend group, I'm a older guy with some older friends (I'm 29, my friends are early to mid 30s) whilst she's 23, and I know because of this my friends wouldn't go near her in a dating sense. Few months pass and we drift apart a bit, we had a situation early November she asked that we go for a walk irl joked of the idea of "having a bit of fun" so I think she was working towards a situationship type deal, but then because of situation we had a falling out that lasted just over a month.

By December she's made a desicion to move away, I was upset but I didn't know the details. Throughout the time she's been talking to one guy the head of the friend group a ton that I don't really compare to, as he's very much a handsome guy and I'm average. Here's the kicker; The main guy in this friend group offered her a spare room to just stay in for a bit until she can find her own place which is fine, but she moved without a job without really much in terms of a safety net to live with him in the hope he'll be interested, as not only that she has a HUGE problem with the girl he's dating.

My crush told me shortly before she moved as we went on a walk together she's compilling evidence against this girl that she's a psycopath even going as far as talking to her ex often to dig up details, she of course left out the information that she's madly in love with him but I strongly suspect she's then going to try swoop in to comfort then try her luck, but he's completely oblivious to this.

The crush even said on the walk it's most likely going to split the friend group, two other friends who we're both close to sat me down recently to tell me what her grand scheme is as theyre very much aware what she's doing and we all do agree it's going to blow up badly for her if she continues this.

What should I do?

Introduced a girl I was seeing into my friend group, now she's obsessed with one of my friends, and is trying to rip his current relationship apart?
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