Cheating??

Okay so this isn’t for me. My best friend of 11 years wanted opinions without knowing who she is. Anyways...

Her and her boyfriend of 4 years have a 16 month old son together. They recently went through a rough patch where she kept trying to leave because he didn’t make her happy or feel good enough and he wouldn’t let her leave because he thought the reasoning was stupid.

Long story short they got into a huge argument and she told him that she didn’t want to be with him at all anymore. They went a couple days without really talking it out and she was super mad at him and in the couple days she sent a nude to a guy that she has known for awhile.

She feels super bad about it now that they made up and he’s doing better to try to make her happy.

Her question is does she tell him and ruin the relationship or just let it go by since she wanted to be done with the relationship and he wouldn’t take no for an answer?