Disclosing Rejection to Co-applicants

[Min K.]

I had a couple (bf/gf in short term relationship) fill out a rental application for a house they're interested in. A simple google search of the male revealed a history of bad decisions ranging from DWI's to a domestic abuse issue. The female has no red flags and makes decent income, but I don't want to rent to them due the males past. All of my dialogue has been with the female. She may not even be aware of these past issues. Am I allowed to disclose to her the reasons for rejection? Or do I just have to tell him....