I have a baby bearded dragon (3 months +/-) When should I start looking to trim her (suspected but not sure) nails? and would it be prudent to just leave some sand paper in her cage so she can "file" them while running around?
If you look at the nails under a light you will be able to see the quik (it is pink), as long as you don't cut pass that you're fine.
Here's a picture of a cats nail, the idea is the same just a different type of nail.
I would be cautious with sand paper, if most of her terrain would be sand paper it could cause some sores on her feet. If its a small area you'll be fine though it wont do much if she never runs on it