My 8 month old boy sleeps standing up, propped against the glass all the time. He's the first of my Dragons to do this, but he's perfectly healthy and fine, so I let him.
As far as your Dragon "Grabbing the air vents off", it's probably just her grabbing at them because she wants something to hold onto, and then they are just falling off because they aren't secured properly. As Cooper said, I'd just let her sleep standing up, that's not at all unusual and as long as she's able to breath and is comfortable with it then so be it, but you do need to secure the air vents with some epoxy (I'm assuming you have a custom, wooden enclosure with the typical type of air vents you see in them, either the round ones or the rectangular ones that usually aren't really functional, but just allow air flow through a hole cut into the wood of the enclosure). I'd just get some good epoxy, like Gorilla Glue Epoxy that comes in the double-syringe container, that stuff is awesome and it dries extremely quickly, I use it on all of my enclosure builds. That way she won't accidentally climb up the wall, grab a vent, and then has it come loose and she falls...
EDIT: What would be a bigger possibility is her ripping out some toenails by grabbing a vent and slipping off of them...