<human>: My girlfriends mum broke down and told my girlfriend that she has been cheating on her husband for over 5 months while we were at a family members wedding. 

She later told her the entire thing, after prompt, whilst sober. She has no plans to stop the affair and both her husband and the person she is cheating on him with work at the same place. She has even said that it is not her husbands fault apparently it's because shes not getting enough time in the bedroom.

The husband is a fantastic bloke I've been on his stag do before him and my girlfriends mum got married. He is so loving towards his wife and their daughter. 

I stand to lose quite a bit if I tell him the situation i will likely end my relationship of 6 years as well as theirs and cause a lot of turmoil on the daughter but at the minute my morals are tugging on my heart strings.

Do I ignore this knowledge that was told to me with trust by my girlfriend or do I go with my gut and give the husband the knowledge I would want in that situation.?

Can you give me the gist of the text in a nutshell?
<bot>: Do I tell an innocent guy that his wife is unfaithful at risk to my relationship or do I ignore the knowledge and attempt to remain civil at social gatherings.