Keep him on the lease. Just because he moved out doesn't release him of his obligation. Do you think the bank will let him off their car note? Nope, not in a million years. Their marital status isn't your problem. Stay out of it and be thankful she's in the position to pay the rent. Make sure to let her know you will not allow their divorce and the drama that usually follows to affect the timely monthly rental payments.
Don't take him off the contract. When it comes up for renewal you can screen her as an individual and then make changes, if you decide.