That's what's called the spider "wobble". From what I've heard they do display it more when they're younger and also when they are excited (usually when food is present). As they get older most will show fewer signs of wobbling. I know that my spider has a little bit of "wobble" but he seems to be doing it much less now that he's getting bigger.

It's not something to worry about, it's not anything that affects their health or well-being. As far as her cruising around her cage a lot, if you just got her she's probably still getting used to her new surroundings and they tend to be a lot more active when they are first introduced to a new environment. I've noticed that my spider seems to be the most active of my snakes however, so maybe it is in some way linked to the genetic "wobble" but I couldn't say for sure lol.