I think that if a woman thinks it, there is a high chance that it will happen with or without her husband's knowledge. Fantasy aside, every single one of us in these forums have a different definition and metrics as to where those relationships can go. Reassurance, trust, communication and clear definition of boundaries (dos and donts is a must). I have heard plenty of cases like Katy above mentioned from women and plenty from men. Each couple is unique they share unique values, desires and wants. The common ground i believe to most couples is communication. If your friend is worried how her husband will react we cal all suggest different approaches in here, but patience, maybe a bit of alcohol, right mood, vacation away from life's responsibilities a bit of teasing and such could all possibly enhance his perception and for him not to be judgemental. One thing though that I can say for sure is the following. In your friend's case, if her husband is not satisfying her, and he is not moderately equiped to do that job his lady will find an excuse, maybe not next month or year, but it is a matter of time, things tend to work eventually. Now if you think about it is it fair for this lady not to be able to fulfill her fantasy? I believe no, is it fair for her husband to be cheated and possibly many times I believe not, hence this is where an open communication comes into play and you newver know. Things can possibly work out fantastically well for your FRIENDS.