It's pretty simple - she is already out there on the trail. The woman you are describing is not the type to sit around, waiting for someone to contact her to go hiking/backpacking. She is already out there. Many women grow up knowing how hard it is to find hiking partners, so we just get out there and enjoy our time on the trail. Anything else just falls into place.
There is also a downside in trying to date someone who only has one common interest - what happens if one of you ends up with an injury and has to stop hiking?