Great thread, guys. I don’t post much on forums but this one got me for some reason. I had the same misunderstanding from my girlfriend about how important riding was to me. She really wanted to try it to have a shared experience, so I bought her a used hardtail for her first bike and off we went to the trails. Learned lessons that may or may not help you but definitely helped us:
1. Be patient, encouraging, patient and patient.
2. Let her learn on her own pace. If she is uncomfortable, nervous, or scared, believe her. We all use chicken runs at some point. No one is ready until they decide they are.
3. Never dart ahead and wait because that doesn’t count as "shared time" mountain biking and like someone said above, it may build resentment (did for me) We ended up having an agreement. A one hour ride together, then I got 30 minutes or so to ride hard on my own. Worked out well because I felt like I got my energy out and we still got to spend some good time together.
4. Let her be her. I learned that my GF is not going to be a great MTBer, but she did discover she really like biking. So much so that she bought a VERY NICE entry level road bike and rides several times a week on the rails to trails. She is a different person with different preferences. However, sometimes I wonder if I had done the above better, she would have enjoyed the MTB experience better and stuck with dirt rather than switching to cement.
Any way you cut it, be happy your significant loves bikes. Chicks on Bikes are hot. You know it, I know it, and now we are with them!
Good luck and thanks for the thread guys.