I can only answer for myself...I'm not privy to the thoughts of ALL women...just my own. I would say, there's nothing to be worried about. And not just because J.T. exists only in my mind, and between the pages of my book.
In my experience, women read romance novels to experience a different kind of romance. This does NOT mean they are not happy with what they have. I've been happily-married for 25 years, together with my man for 28. We have raised 4 kids to young adulthood. We schedule weekends away as often as we can afford to, in order to spend time just being with each other. He's very romantic, and still to me, the sexiest man I ever met.
But not only do I READ romance novels, I WRITE them!
Why? Because even though I would never cheat on my husband, whom I adore, I still have fantasies in my head. I still imagine what it would be like to be with other men...I see someone walk by, I see a face/body on TV, or more commonly for me, I wake up with a whole storyline in mind, that involves me being some other woman, and meeting some other man, who turns out to be the one I've been looking for.
Why do men look at pictures of naked or scantily-clad women? Same reason. And just as looking at sexy women might "put them in the mood", so too do women "get in the mood" reading stories about another woman's love story. Don't worry about HOW your woman got in the mood, guys. Just enjoy the fact that she is, and that she's turning to YOU to scratch her itch! Happy Valentine's Day to everyone!