It's great that she wants to join you! I also understand your concern. Touring with somebody else (or in a group) changes the dynamics of the tour. It's no longer only up to you when and where you will take a break, have lunch, or camp for the evening. It's a compromise, and in a group you're also only as fast as the slowest person.

I wouldn't put limits on what she can do, but express that you don't want to wait on her anymore than she wants to wait on you. Set aside some time each evening where you can do your own thing: She can blog, and you can do whatever you want. There's no perfect solution, but remember this is also her tour.

Heck, if you have an iPhone then check out TrackMyTour. It's a location-based micro-blogging app that I wrote for bike touring. Updates take seconds - which is something my girlfriend appreciated during our tour this summer.

Have a great tour!