I'm jealous that you can get her to bike w/ you. My boyfriend hardly ever rides w/ me, and when he does it's such a rare thing and I'm so excited that I don't mind going really slowly so he can keep up. He's usually so grumpy about it, and complains so much that's it's almost not even worth it (must be some weird man ego thing. ugh.).

Maybe it's just best to be patient and enjoy the time that you are able to spend together on bikes. Don't pressure her, whatever you do, or she'll hate it! Would she be mad if you rode your common commute separately a few times a week so you can ride at the pace you enjoy?