I (30M) am in a position a friend has placed me and I hate it.

A friend (41F) ended an abusive marriage with alcoholic (41M) and talks trash about him to our shared friends but is secretly dating/having relations with him and only told me. I am expected to keep this secret from our other friends and I hate the position this puts me in.

When other people ask if she’s dating again she tells them no because her old marriage was so bad and how much damage his alcoholism did to her family but she will privately tell me she is romantically seeing him again. She tells the world she is spending holidays alone but will tell me she is spending sexy time with him. When this blows up and is revealed to our friend circle I don’t want to get sucked into this mess.

I don’t know what to do. I have bluntly told her she is “happier now” because she is no longer living in the same space as him and doesn’t see the alcoholism because of this. I have told her the other friends will feel betrayed when this gets out to which she responded “yeahhhhhhh…..” She “loves him” and wants me to go along with her telling everyone she’s single and looking as well as talk trash about this man in public because “no one else gets creating a family with someone.” Oh and he is apparently still drinking.

Do I keep this secret? Do I not? It’s not fair to myself or the other friends. I don’t know if she is stuck on “we have grown kids together” and can’t let go or if she is codependent or what. I bring this up because her oldest kid (19M) has mental disorders to the point where police are regularly called to the house when he does not take his medication due to violent behavior and she sneaks medication into his food because he refuses help (story for another post).

Please help the situation. Do I keep the secret knowing I will be disliked by the other friends when it eventually comes out or hold an intervention with this person? Do I tell others? Thank you Reddit family.