i know it was mentioned they were blackout drunk, but to me i feel like if you are subconsciously thinking about that and vocalizing some stuff WHEN YOU KNOW SOMEONE IS TAKEN, somewhere in my gut believes they’re the type to not care about being “the mistress” whatever you may call it. its very disrespectful to me that she said that to your bf especially when you weren’t around.
i would obviously consider talking about this with them, but you may take some time to earn trust back. and that may not happen.