So I have a friend ( we’re gunna call her Sally) that I’ve known for a good year or so. She has been dating some dude I know for the past 2 years and they have developed such a strong bond.

Well I recently found out that she starting falling off track with her relationship and admitted to having feelings for another dude.

The thing is that I also experienced this in my current 4 year relationship when things began going downhill.

I just need help/advice as to why women develop feeling or go off with another person when things starting to go to shit in a relationship??