I posted a few months ago about my friend who confided in me she had started seeing a guy (lets call him James) who was already in a long term relationship and had 2 or 3 children (can't remember which) and that the youngest was only a 4 month old baby.
When my friend had first met James she wasn't aware of his situation and only found out for herself when she looked him up on Facebook and found lots of 'Happy Family' photographs of him and his partner (lets call her Katie) etc. My friend confronted James but continued seeing him as apparently they '"had something special'"
Anyway - I saw my friend again today (I had withdrawn from her a little because I felt uncomfortable about it all) and she told me she had realised she was in the wrong and that last week she met up with James for the last time to tell him it was over. She said she'd been telling him this for some time via phone calls but because he'd been continually ringing/texting her she had met up with him face to face to make him see how serious she was and make him realise that him contacting her had to stop.
However, James continued to text my friend and leave voice messages on her phone etc saying he wanted to see her and he didn't want their affair to end and as a result my friend decided to tell Katie what James has been up to!!! Last night my friend sent a message to Katie via Facebook and told her that James has been cheating on her for over 6 months and relayed what James had been saying about his 'unhappy relationship' etc. My friend wrote in the message that as James had continued to harass her after she'd try to end things she thought it only fair that Katie knew what type of man she was with!
I was 
She had not previously threatened to do this - i.e James had not been forewarned that unless he accepted it was over then my friend would tell Katie what was going on. My friend just took it upon herself to 'break the news'.
I'm all up for cheaters getting their comeuppance but all I can think about is poor Katie, opening up a Facebook message and reading that!! Can you imagine receiving a message from some random woman claiming to have been having an affair with your partner of 8 years who you have children with, let alone a new born with!!!
Would you have done that???
AIBU to think that maybe it wasn't the best decision my friend made??