Another bit to consider is if she is fast enough to ride on the street.

Some people are just perfectly happy with cruising along as slow as humanly possible. one of my old roomates was like that...he would get on his red madwagon and just move at literally walking speed for hours on end...he just liked being on a nice cushy seat, with fat soft tires, and just strolling up and down the blocks. No problems at all with that.

Maybe she just likes moving at that pace as well...at that kind of speed, being on the road is pretty much asking for trouble. As much as it sounds unlike me to say it, but it's true...you gotta be going so fast for traffic, just to give them enough reaction time to deal with you.