1. Make sure her bike fits her well, and don't hesitate to buy multiple saddles for her to try.
2. Don't make faces if she buys a lot of cycling clothes.
3. Get her a custom bike, and let her design the paint scheme.
4. Put an electronic group set on her bike, to make shifting as easy as possible.
5. If she asks to go for a ride, forget about your training ride and ride with her instead.
6. Let her set the pace on uphill sections. You can pull on flats and downhills, but make sure she can stay on your wheel.
7. Give riding tips sparingly.
8. Clean and adjust her bike regularly.