Educating yourself and being prepared to be a responsible pet owner are all things that will help to make you the perfect Pit owner. Please, do yourself and the dog a huge favor, and have it spayed or neutered as soon as possible, and spend as much time with your dog as possible. Never forget it is a DOG, not a child, and not a play toy that you can put out in the back yard and forget for days on end, or chain up and leave to its own devices, that is a death sentence for a Pit, because they will become angry and you will ruin them.
I have dealt with plenty of dog bites in my former career as a deputy sheriff, and the vast majority were dogs like labs and heelers, but they were mostly dogs that had been neglected or abused or treated like kids and were spoiled. I have to admit to originally having the same fear that your mom has, but that fear is not about the breed of dog anymore, but because of the typical owner. Do yourself a favor and get her some videos of Caesar Millian,(the Dog Whisperer) and the pit he works with named "Daddy", they are both great ambassadors for the breed.
I have 2 very large dogs of my own, that scare the snot out of people because they are large and noisy, and one of them is pretty aggressive, but he knows I am the boss around here , and he is in no doubt that I rule his little world. You have to make sure that your dog has that understanding from day 1.
Good luck to you, and if you ever need any help with your pup, shoot me a line, I have been working with dogs for over 20 years and both of my big boys outweigh me and could eat me for lunch, but they are big sweethearts and my babies roll all over them.