Kiel: One way to view differences in interests is as "the price of admission" to the relationship. Since you're not going to find anyone who is 100% compatible in everything you do or like, are the differences an acceptable "price of admission"? By which I mean, why isn't she willing to gladly pay this small price for the benefits it offers to you and therefore your relationshi? And really, WTF is a less objectionable hobby than backpacking? The gear is cheaper than golf, hunting, boating or flying. The activity itself is healthy, unlike bar hopping, partying, or eating out and is far less injury prone than running, tennis or bicycling. And if it clears your head, it is about $125.60/hour cheaper than a therapist.
To be blunt, her unwillingness to hear why you enjoy doing this and how you could minimize the already small risks starts to sound more like a generalized fear of the unknown, extreme neediness/narcissism, or pretty controlling behavior. Which maybe begs the question what price of admission are you willing to pay?
But YMMV (your marriage may vary). My wife is rowing right now on a cold Alaskan lake on a very windy day in a 11-inch-wide boat. And we'll be hiking up a grizzly-infested valley to the terminus of a glacier with our grader-schoolers this Saturday. To each their own.