There is a contradiction that if we go to the vampire route at the before we go to Fallhalt,we don't know what will happen toAnja.so I think it is better to put the side quest "A Simple Delivery"at the end of chapter3.
It's not a good idea to reproduce what happened in the main route,new place should be added into the vampire route rather than simply bring Mila back to where she should go in the main route,vampire route is a new and cool routse right?