The Light We Found by Q.D. Purdu

I enjoyed this short novella, about a divorcee who's daughter just can't shut up about her dad and his relationship with the other woman. Calla's life bears bad news, so she goes back to teaching. Her student she is tutoring has a breakdown and she calls in his parents to find that it is Ben the man whom came on to her in dancing class and he told her he was married. This is where we find out the truth.