What is the legitimate Islamic solution to this problem, and is it permissible to compel a wife to abandon her studies, or to marry another, knowing that the goal is chastity and avoidance of temptation?

If the legal marriage contract has been concluded for you with the girl, then she has become your wife. Her guardian does not have the right to postpone the completion of the marriage or prevent you from consummating the marriage after the dowry has been handed over, unless that was stipulated in the contract. If you have paid the dowry, then he does not have the right to postpone for the purpose of her studies. Otherwise, he has the right to prevent you until you hand over the immediate dowry. The best approach is a calm dialogue to reach a middle ground that achieves the benefit of completing both the marriage and her studies, and you can promise her that. If he does not agree, then comply with him unless there is harm to you in doing so. Marrying another is permissible, but if you can be patient until this marriage is completed, then do so.