Do you think I should speak up?

So, I have a friend/coworkerwho slowly has been destroying herself and turning into a really bad friend. She's always been one to make those stupid passive aggressive posts on social media that range from "omg I'm so beautiful fuck the haters" to "absolutely no one loves me, please feel bad" but that was only annoying and could be looked past cause lets face it, a lot of chicks are like that and as long as the chick is cool in person/to me IDC. She was so close to me I had her in my bridal party when I got married last year. Our friendship has been basically demolished. I used to host game nights at my place once a month where we would drink and play cards against humanity or whatever. She would come most times but then she started alienating my friends. She once brought a dude she was dating and got in my others friends face for literally just looking at him. She threw a fit because two of my VERY SINGLE friends hooked up. She stopped coming to things and started blowing me off so I figured she was just busy or whatever. BUT we had sushi about 3 months ago because she wanted to makeup for being a crappy friend. She was just shy of two hours late and only wanted to talk badly about her life. So at that point I figured our friendship is dead. Whatever right?

Well, the dude she brought to the game night must've really done a number on her cause she still to this day talks about it AND obsesses over him. (Been over a year now) See, he's a coworker too. She's now going around accusing people of sleeping with him which even caused one girl to be pulled in by management to ask if it was true and another's husband banned her from talking to the guy because he was afraid it was true. She's making everyone at the office dislike her but more importantly she's gonna get her ass fired. Should I try talking to her about it to see if some sense can be knocked into her or should I let her destroy herself?