Yes, it is due to incorrect disbudding when they were smaller. However, some goats do just have stronger horn growth than others, and even if disbudded correctly can have a bit of regrowth. You often find that males have a lot worse scurs, as they have a much stronger horn growth.
It depends on how much her horn grows. You do need to keep an eye on it, because it can grow right back to her head and dig in. You can trim it down, the vet will do it for you if it grows too back into her head. One of the easiest ways to do it is by using cheese wire, and cutting through it.
I'd advise getting someone else to do it for you if you've never done it before. If its just a wee growth and feels quite wobbly to you when you wiggle it, then it will probably come off by itself.
I can't find any pictures that show my billy's scurl, otherwise I would post a picture.
Beth