I'll even go a step further: I'm willing to bet that this woman loves her man, and they are indeed happy, but not as happy as they could be.
There is cognitive dissonance happening here due to the fact that Watchtower keeps repeating to her that inter-faith marriages don't work, despite her being in one!
If her husband forces her to confront that paradox, she will double down on one side over the other. If she doubles down on recognizing that she is in a happy, loving relationship, she will feel liberated, and this will result in even more love and happiness.
I've known a JW woman married to a non-JW. At the Kingdom Hall, many treated her as a victim. For years, I've seen her act as if she remained with him because "marriage is sacred." Then, when the man took his retirement, something changed; they did many more things together, and that loving spark grew between them until he passed away years later. My point is that all those 20-some years before that, she could have accepted the fact that she loved him and wasn't a victim of anything but love. They could've had 20 more years of that loving spark.
In the end, JWs say with their lips that "marriage is sacred," and then willingly destroy the joy, love, and happiness out of inter-faith marriages. You want to say that a marriage is sacred? Then make sure it is a priority in your life, and you keep that loving flame burning.