Anyone had an affair that developed into a 'propper' relationship?

[Aniles]

My single friend started an affair with a married man a few months ago. At the time I tried to warn her off but she was adament that it was just a bit a fun, she knew he wouldn't leave his wife and kids and she accepted that. She said that she was happier having a casual no-strings fling rather than have to deal with the problems she has encountered in the past with real relationships (she has had a few bad 'uns!). He gave her the usual 'I'm not happy, just staying for the sake of the kids' talk and I gave her the 'they all say that, he's just using you, you (and his wife) will end up getting hurt' talk.

Now the inevitable has happened! She's fallen for him big time and he's talking about leaving his wife. From what my friend has told me he has actually taken steps towards doing this, so it doesn't seem to be 'just' talk.

I'm really worried about my friend getting badly hurt. Obviously I feel bad for the wife and children (I've been cheated on myself) but my friend is my friend and I love her. Has anyone had any experience of an affair developing into a real relationship? Does it always end in tears for the 'other woman'?

Thank you everyone for your (very) honest replies. I've talked to my friend some more but nothing I say will change her mind about what she is doing. I can't do anything about any pain and hurt that might be caused to the wife, which I do feel bad about, so it looks like I'll just have to hope that the situation doesn't drag on too long and that it doesn't end too badly for all involved x

My FIL, just to set the scene was celebrating his 28th year of marriage with my MIL, whilst seeing a model. Now this model was very tall, blond and leggy and was......................39 years old when they started seeing each other. My DH found out his fathers secret when he visited just by chance as his parents always had separate holidays, he would go golfing to Portugal, she would be doing a cookery course in Spain, I think you get the picture. When my DH pulled into his fathers driveway, he saw his dads car, engine running, drivers door open and no-one in the car, so he walked round the house (after switching off the engine), then he heard his father say, "I'm sure the engine was running", my DH appeared in the front doorway, only to discover that his father wasn't going mad talking to himself, but was talking to this strange woman, who he was practically wrapping himself around as they were walking towards the front door, my DH was extremely angry and a slagging match ensued, with my DH slapping his father and said that if he was going to leave his DM, then he had better do it as soon as she came back from her holiday, otherwise he would tell her. His DF told his DM, a separation of a couple of months happened, his DM got depressed, his DF got married to the "Other woman" and 2 weeks ago they celebrated they're 3rd wedding anniversary, how long had they been seeing each other, you may ask,.......
14 years and they are so happy now and she still models, she was in Good Housekeeping after wining a modelling competition last year, aged 64. My DH can't forget what happened and sometimes it takes him a while to come round, but my step MIL has made my FIL a very happy man. I am not saying what they did was right, and if my DH did anything like that to me I would make sure he could never bonk again, but it's like a fairytale come true for them and they love each other so much. My MIL is still a very bitter woman, she too got re-married and it lasted almost a year, he lives in London and she lives in Yorkshire, they refuse to live together, but spend a few weekends together, they say they will never get divorced..............