I read recently about a Jewish woman raped in France at home in front of her husband. If Chas VeChalilah a wife of a Cohen is raped, they have to get divorced.
Would it be advisable for an unfortunate Cohen whose wife is about to be raped in front of him to look away and block his ears? Would that help them stay married as he could never know if the rape actually happened?
In general, the principle of "kim li bgava" -"I believe her" means that even where she doesn't have legal reliability otherwise, if he himself does think she's telling the truth, he's no longer allowed to be with her. That would imply there's no wiggle room for a kohen in such a situation since he presumably does suspect what's going on. Not to mention that she herself knows, so would herself presumably be forbidden to be with him. (Though there does exist a very novel opinion in the Achronim that if he doesn't have to believe her, she's not under her own independent obligation to flee him.)
The Micropedia Talmudis reports:
יש שכתבו שאשת כהן שנתייחדה עם נכרי אפילו פעם אחת, אסורה לבעלה אף אם אין רגלים לדבר שעל דעת זנות נתייחדה עמו (יראים השלם מה, הובא במהרי"ק קס); ויש שכתבו שאף אם נתייחדה עם נכרי אינה נאסרת, שאף על פי שהנכרים פרוצים בעריות הם, היא בת ישראל ואינה בחזקת פרוצה בעריות, ולכן אין לחשוש שנתרצתה לזנות (פסקי ריא"ז כתובות א ג; בית משה אבן העזר ז יא; אבני נזר אה"ע טו יג; וראה במהרי"ק שם).
There are those who write that the wife of a kohen who was secluded with a non-Jew even once is forbidden to her husband even if there is no reason to suspect that an immoral act took place. And there are those who say that even if she was alone with a non-Jew, we do not have to suspect that something took place.
I suggest your question could be similar to this case. In both cases there is no evidence. So the case is undecided.
Her testimony does not harm her as it says:
אשת כהן שאמרה לבעלה טמאה אני לך, שנאנסתי מאחר, בראשונה היו אומרים שנאמנת, ותצא ותטול כתובה, חזרו לומר שאינה נאמנת, שלא תהא אשה נותנת עיניה באחר ומקלקלת על בעלה בשקר לומר שנאנסה (משנה נדרים צ ב). הלכה כמשנה אחרונה שאינה נאמנת (רמב"ם אישות כד כג, ושם איסורי ביאה יח ח; טוש"ע אה"ע ו יב).
If the kohen's wife says she was forced by someone, originally she was believed and she lefthim and got her kesubah. Later they taught that she is not believed so that she should not use this as a pretence to leave him for another with her kesubah. The Halachah is like the later teaching.
