A long term work to tackle.
Much of the advice given so far is great as far as im concerned. Always make her sit and stay while feeding, sometimes place the bowl and leave her sitting for a few minutes.
Feed her a perfect timed intervals so you always control the distribution of meals.
Other genral things help also. If she climbs up or comes to get affection, push her back, make her sit and ingnore her for a second. Then call her to you and give her the love. Reinforce the understanding of you being in control in a way she respects.
If she sleeps on the couch, make her get off everytime she climbs up by himself, and then when shes sat and stayed to your satisfaction, give her the up command (some trainers say dont let them get up because height and dominance as connected, however ive found it much more rewarding for the dog to realise that soft comfy couch is ok but I get to control the ups and downs. My dogs gerneally ask me to get up on things!). Again, help him understand its not what he does thats at stake here, just the fact that you are the one who says do it.
Its healthy with a dog to randomly request obedience throughout his or her day. This helps them to remeber whos the boos and respect you without agression.
The worst thing you can do with this dog is slap them, hit them or show aggression. The position they have is one of challenge, they respect you as dominant but in a dog way, meaning there are limits and they will lay down a challenge for things like food, bones and objects they prize. Not a healthy chain of command with a powerful dog.
ou have to work to turn that into a relationship of provision. SHe must understand that you provide for her, you feed her when you want, you let her up when you say so, you pet her when it pleases you. The more she understands this the more she will find pleasing you a good thing and respect your authority to boot.
Dont let her behave with ill manners to you, if you feel shes behaving obstinately, or rudely, let her know, make her sit make her stay, spoil her fun and then when you are satisfied shes listening, give her love again.
Its a day to day role, but with time if you always remeber not to accept rudeness or arrogance from her, she will start to learn from your position and be more respectful around you.
Its VERY normal, it likely means she views you as an Alpha dominant, as I said that may be useful with a toy dog, but with a Pit...well do you really want to reinforce alpha dominance on her when she decides to challenge for leadership? I wouldnt thats for sure!!
SHe must understand she NEEDS you, you provide for her, you care for her and you call the shots, also that she can never be the leader! Be firm, be fair and be kind and she will respect that.
I hope its helpful, im not a pro trainer but ive self studied dog training for many years and tired many different method out so the info I have is at least well informed, if its of any use then great, if not, well I can only offer what I have to give.
Good luck!