It's not safe to assume. After being on the shot for 1 year, It took me 6 years to get pregnant. With my friend she was on the shot for 4 years, and she got pregnant the 4th month after she was off the shot.
I have never and will never cheat on my husband. However I think women and men cheat because they are feeling that they are lacking something in their marriage...Whether it be physical, emotional, affection whatever.
Maybe she is afraid to go to court? In that case there can be a waiver of court appearance in the documentation of divorce decree, where all she has to do is sign and he shows up to court, done deal.