It all depends on what was told to the police. Did she explain what happened to the police, or did dad speak in her stead? If she is not speaking to the police, that would cause some problems in any prosecution.
As suggested, she needs to get her injuries looked at, treated, and documented immediately. The longer she waits for a professional to evaluate her injuries, the less likely they can be used against him. If there was a significant delay between the time the assault occurred and when she showed up at dad's house, that might explain the difficulty the officer was trying to explain. Time delays give a defendant the opportunity to argue, "When she left me, she was fine ... maybe she beat herself up to frame me!"
The police will want to talk to the guy that she was allegedly flirting with, and they will want to speak with him. They will also need that medical information. They will also want to review the ATM video where she or he withdrew the funds. She should contact her bank to change her PIN and to report the robbery to them so that she might be compensated if they offer that as an option for their customers. She should also immediately obtain any records of the transaction(s) made to prove that the money was withdrawn where she claimed because any video might be days or weeks in coming even if the police seek a search warrant or a subpoena on Monday.
Given your explanation, I cannot see why the officer would say that a prosecution would be unlikely. This leads me to believe that SOMETHING about the tale, the injuries, or the events puts the facts into question.

