I don't (personally) believe that one becomes more sensitive to gluten - either you are sensitive or you not. I do believe that symptoms can become more obvious and uncomfortable once you actually become healthy. When you eat a food you are sensitive to, a body will "mal-adapt" so you can handle constantly being ill or in pain. The body makes illness the new normal so reacting to a hot dog bun isn't as obvious of a hit to your health because you are already on a much lower level of health... does that make sense?
I don't think there are sensitivity levels to gluten either, just a wide variety of symptoms that vary in severity.
I do hope she comes around. Good luck to you!