Best friend is addicted to male attention
And her drinking lowered and lowered her inhibitions until she was drunk (right?) and grinding some guy who wasn't her husband and who mattered to someone she was supposed to care about. There may be two dependencies here.
Knowing you can't trust her is the easy part; she has made it plain.
Whether you choose to distance yourself from her over this, or instead to see her as still your friend in her flawed and compromised and compartmentalized way, is up to you and is much more complicated.
But I urge you to say your piece about her behaving like an addict when male temptation is present -- and about your being codependent, which also isn't just about substance abuse. Ask her if she can see her role and yours in shielding her from the consequences.
Thereafter, when she does this, say you won't be a party to it and then disengage. For the night; for as long as you need to cool off; for good. Your call.
Finally, you were available but your crush opted to grind with the drunk married mom friend. I hope he's looking a lot less crushy today.
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