If you can get her to tell you anything about why she is embarrassed, it would be a good start. I hate the thought of it, but maybe she was mutilated earlier in life. I know it happens to women, frequently in some cultures. I hope that is not the reason.
Tell her you and she are husband and wife, two people who will always love, protect and look out for each other, and any part of her mind and body is sacred to you, as yours should be to her. And if you can only trust one other person in the world on that level it is each other.
If that doesn't get you fucked, I don't know what to say.

Don't lose your sense of humor.

BUT IT'S THE TRUTH!
(or if it is not the truth, it should be)