Running together, at her pace not yours works with my wife. Slowly but surely she is coming round to liking it as an exercise form, in addition to the bike commutes and Zumba and pilates. Essentially as all the others have said, encouragement and trying alternatives are a far better approach than goading and forcing things on people.

So all in all she’s pretty active really, she just suffers from me being a good cook too!

Favourites among non mountain biking girls I know are
Zumba and other dance type classes (Streetdance I think, Jazzercise, is that a thing?)
DVDs like “the 30-day shred”
Spinning (but won’t come for a ride with ME, wahhh)
Running (almost every one seems to be on facebook going on about running)
Walking
Yoga/Pilates