Yes, they can do that. It is not uncommon for police in another jurisdiction to do a courtesy interview for another agency when the victim has been relocated. Usually they do this to gather information interviews for the other department. If the officer is going to testify in court then he would need to come to Texas to do so. But often they do not since to make the case the victim herself would most likely need to testify.
From the information you've given, it looks like a normal investigation that involves a victim who lives in another state. Things can be more complicated when there is actually a trial and witnesses have to be present in court due to constitutional requirements. Your brother should retain an attorney in this case.