In my experience, the more urgent a person feels they "need" to connect with the dog, the longer the dog will resist it. Best bet is for your dad to stop wanting to connect so badly, give the dog its space and let it make the first approach.
Is there some reason that you "believe" the dog was ever abused, or abused by someone similar to your father? Many times people assume this type of thing and then treat the dog with "kid gloves" so to speak. In other words, show her innapropriate sympathy, which in any case is not so helpful! The sooner you get over that frame of mind the better, because it won't help your dog!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain