How do I handle falling in love with my wife's best friend?

I've been with my wife for 10 years now & married for 2. Her best friend, call her Meg, has always been flirty and considered herself to be the third wheel of our 'tricycle'. Meg hasn't had any boyfriend last and is tanking a break from dating. She jokes if anything happens to one of us, she'd marry the other. Meg even talks about what our baby could be like since my wife might not want kids and I do. Even Her mother refers to us as the theeesome and that we'll always be together.
What's hard is I love my wife, but I'm finding myself thinking about Meg more and more. She's always making more eye contact, trying to sit next to me, more touchy with me, jokingly holds my hand while my wife holds my other, and hangs on my shoulder. The same stuff my wife did when we started dating. All her body language has gotten more frequent and noticeable. I think I'm falling in love with her.
When my wife and I are havin sex, she fantasizes having a threesome with Meg and I play along. My wife can be jealous, she hates my female coworkers, and talking about Meg having my children. When we go out or friends come over, my wife has me walk Meg to her door or car, but no one else, we live in a good area.
We had a party with a bunch of GFs from HS. They claimed the couches, guest bed, and said Meg should sleep with us. My wife and Meg said I gotta sleep in the middle calling me a 'true manwich'. All clothed and just cuddled. I never slept better in my life.
What the hell do I do? I love my wife, and making her happy. I feel great when Meg is around and seeing them happy together. I hate hearing Meg put herself down cause she can't find 'a guy like me'. I'm not special, I just try to make everyone happy. A threesome with them would be amazing, but I don't want to risk my marriage or friendship.
Do I tell my wife I'm falling for Meg? Do I suggest we actually have a three way? Any suggestions on a successful three way? Can bigamy work outside the law? I'm lost and don't know who to ask.
Updates
+1 y
So having been limited by characters, there is a bit more. Meh has always referred to me as her 'twin' because of how similar we are and she has used me as such to get out of bad dates. I'm also not 100% certain of her feelings towards me as she is usually VERY introverted. I'm also respectful of my wife/chicken shit to talk to her outside of group texts or group environments. There have only been a few times where we were 'unsupervised' and we just awkwardly bullshat like nervous little kids.
How do I handle falling in love with my wife's best friend?
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