Since you two have a handicapped child together, I would suppose that the best thing is to try and stay together....I have a question for you...why would you do something so cruel and vile as to sleep with his best friend. I mean of all the people you could have picked to have sex with, you picked one your BF's best friend. That is just cruel. Do you harbor some hatred towards your fiance? Your choice of affair partner is not a mistake.....this was done in part to harm your fiance...the question is WHY?

I'm certainly not defending her actions, and from reading HNHN, its very clear that a best friend is a very likely person to be the target of an A. That person was around a lot, filling some of her ENs and building up a balance in her Love Bank. Its the same reason why it happens with coworkers a lot. Just because they are around a lot and get to meet ENs without the pressures of dealing with everyday life. I'd guess she didn't just wake up one day and decide to have the A. I'd guess it built up over time.