It's been a while since I did an AD, but from your description, Maggie shouldn't have any problems.
Are you using a bike attachment? The dog has to run on the right side of the bike, so make sure Maggie is used to the right side and is comfortable with it. The biggest problem dogs have with ADs is bloody paws - either they got it cut on something, or they got rubbed raw from running on the pavement. If there are grassy curbs or dirt shoulders anywhere on your route, take advantage of those and get Maggie to run on them. During the breaks, the judge will be checking the dogs' paws for bleeding, so make sure Maggie is comfortable with you picking up her paws and another person leaning over to check them out.
I wouldn't do anything special right now leading up to the AD. If she can do six miles without any issues, she is fine. I'd just keep biking two or three times a week. What I did when I was conditioning for the AD, was do shorter trips (2 or 3 miles) on weekdays and push for speed (but still at a trot), and on weekends when I had more time, do longer trips at a more leisurely pace to build for stamina. I trained mostly on dirt roads, and would do 15 to 20 minutes at a time on blacktop to condition the paws.
Good luck and have fun! I think after doing an AD with Gryff I'll quit the AD's because my arthritis makes biking hard now.
But when I trained with Keeta, I loved the exercise, bonding, and the satisfaction of working together towards achieving something. Plus, going out with other club members to do actually do the AD was a ton of fun too. So relax and enjoy!