It is true that Islamic countries need alot of reform but the majority of Muslims do not apply what's in the book word by word.
In Islam, the only 3 reasons given for killing another Muslim is, adultary, killing another human (eye for an eye...) and abandoning Islam. However, it is also said that a person shall only be killed after being judged. Also, and this is important to know, there is no Islamic law that permits a person to take the authority of a judge in his own hands. A person cannot try another person and condemn him to death, only a court can. Therefore the term "honour killings" in Islam in basically utter tosh.
Now, I'm not saying that these laws are not shocking, they are and that is why I started this post by saying that Islamic countries need reform and as I've said many times, the Koran was written in another time and another context. What seemed fair at that time, looks shocking in our time.
That said, there is no proof that the father threatend his daughter, but yes, even if there is a minor chance that she might get killed or hurt, she should not be returned to her family because these crimes, due to IGNORANCE, do exist.