What is the ruling on a father preventing his daughter from observing voluntary fasts under the pretext of fatigue and inability to concentrate on her studies, along with his anger and shunning of her when she attempts to fast?

If your voluntary fasting angers your father and leads to a rift, then you must obey him, because he has a reasonable intention in prohibiting it. If the father is significantly harmed by the disobedience of his command regarding a permissible act, then the child must obey him, unless the father's command is mere foolishness, in which case it should be disregarded.