I've had my dragon for about a day now, and I've been frantically looking things up left and right to see if I'm doing everything alright, but I've never seen this mentioned.
She just hangs off her rock like that near the basking light, and chills out. Whenever she wants to, she'll get up onto the rock and move along, so I don't think she's stuck, and she'll just be near the edge, and back off so she can hang. I'm not sure if this signifies anything, but if it does, it'd be good to know!!
Sometimes they are comfortable sitting upright like that. It's fairly common. One thing I'd check is the surface temp right on the top of the rock. If that's too hot, then she may be sticking to the side to enjoy slightly cooler temps and avoid the high heat.