This is unfortunately not unusual today, especially in light of societies complete perversion. It is known that even straight women who are exposed to pornography on the internet, can develop an attraction for other women. I don't know if this is the case with your wife, or if she just naturally feels this pull. In any event, it is perhaps no less common than men being attracted to other men. I have heard of cases where the wife's SSA (Same Sex Attraction) ended up destroying the marriage. She should be warned that it has the potential to destroy the marriage and she should be careful not to act on her feelings. Just like when men are attracted to 'married women', as immoral as it is, we are programmed to have these feelings. In the same way, some people find that their brain is programmed to have SSA feelings... The bottom line is though, we DON'T ACT ON IT.
Have your wife read this article from Arutz 7: "
How I almost Became a Lesbian".
In case you want to know Judaism's stance on this, see
Rambam, Hilchos Issurei biya, Perek 21, 8-9:
ח) נשים המסוללות זו בזו--אסור, וממעשה מצריים הוא שהוזהרנו עליו: שנאמר "כמעשה ארץ מצריים . . . לא תעשו" (ויקרא יח,ג); ואמרו חכמים, מה היו עושים--איש נושא איש, ואישה נושאה אישה, ואישה נישאת לשני אנשים.
ט) אף על פי שמעשה זה אסור, אין מלקין עליו--שאין לו לאו מיוחד, והרי אין שם ביאה כלל; לפיכך אין נאסרות לכהונה משום זנות, ולא תיאסר אישה על בעלה בזה--שאין כאן זנות. וראוי להכותן מכת מרדות, הואיל ועשו איסור. ויש לאיש להקפיד על אשתו בדבר זה, ולמנוע הנשים הידועות בכך מלהיכנס לה ומלצאת היא אליהן.
Also, some of the articles and links on
this page might also be helpful for her to read. Although they are geared mainly towards men with SSA, many of the links and articles can apply to a woman with SSA too.
May Hashem be with you.