Camille's exclusive source of mitigation is her passive, a 20% max HP shield which is... kind of a lot, actually. It gives her a better defensive steroid than Ornn, Sion or Nautilus which is... odd. Only protecting against one type is irrelevant as long as the shield is completely consumed or your opponent does only that kind of damage.
That said, this:
she can usually basic attack other top laners to death in the levels 1-3 with no issue
isn't really true. She can win trades early but struggles with extended fights, especially levels 1-2 where she does not generally have her Q. Her laning phase is below-average (although not awful) and she scales well into the mid game since she spikes hard off of certain items.
If you want to compare her to Fiora, which is probably her closest mirror in terms of what their kits do (mobile, AA focused true damage dealing), she has identical base AD with ever so slightly higher scaling (0.2 AD/level). She has 2 more base armour and 25 more HP.
She's probably a little too tanky. The nerfs on PBE to runes she takes (Chrysalis, Bone Plating) are going to help reduce that but a lot of other top laners are taking the same so probably won't impact her that heavily.