OP here.
Thank all of you for your thoughts and suggestions.
As Keim pointed out, her recovery process is a complicating factor over the "just say nothing ever", which is my usual policy for gifting money to friends and family when they think are taking a loan from me.
I am going to tell her that she does not have to repay the loan and should consider it a gift. If she wants to return the gift, she should do so only as an act of joy--or better, pass it on to our child as rent repayment.
I don't know how to navigate the "hold her accountable" as a part of her recovery over "keep the worry hanging over her head", so I'm going to try to remove the worry and transfer her moral obligation to helping our child.