I think this is easier to deal with tbh - if he and DSD can slowly rebuild their relationship it will probably be more genuine and lasting than if she ran away from her mum and he was the only person to run to.
It also gives me time to prepare DD for DSD being an active part of our family (and deal with myself!)
I just hope that DSD doesn't fall into the trap you experienced and blame herself for the abuse she is subject to 