I have a very young female cockatiel named Sushi.
I would like to train Sushi to be friendlier; however, she never comes out of her cage, and when she finally comes out, she bites me. Sushi doesn’t just do a quick bite like other birds; she clings on my hand with her beak and causes me to bleed (I even accidently ripped off neck feathers trying to pull her off once). I want to train Sushi to be a friendly and loving bird, but I am too afraid to even touch her, Can you someone me?

Wear gloves or something on your hand to lessen the pressure of the bite as you train her.

The trick is to build a positive association with your presence. She should see your hands as a source of feeding and nurturing, not an object to defend herself against. Has she had other owners in the past? If so, perhaps she has had a bad experience with another person that would cause her to build such a poor association with hands and people in general. Place food in your hand and hand feed her. A good method is this: Instead of placing her food bowls immediately back when you replace her food, keep them somewhere distant and instead hand-feed her. A commonly loved treat of cockatiels is millet spray. Take her from her cage and hand-feed her the millet spray. When she bites, you simply wait two minutes with her on your hand before giving it back. You remove the treat for one to two minutes everytime she bites, and when she has calmed you treat her again. This is a gradual process that takes patience and understanding on your part as a bird-keeper, and parrots are exceptioanlly intelligent when it comes to building both positive and negative associations. Reward good behavior, and ignore bad behavior. Remember to always take her out of the cage, and resist the temptaion to scream, because this encourages biting. Make her cage full of toys she can tear apart and be very kind to her, always :)

Personal birding experience

I learned this from a pet store that specialized in really well trained and sweet birds. It is difficult at first, but grab her beak at the top (not her nostrils) with your thumb and first finger and squeeze, while saying "NO" sternly. It does not feel good to her, but it does not do any damage to her beak. After you do it a few times it will work to stop biting.

hire some one to go through steps with you . if you are afraid at any point near her she will feel it and bite.

personal experience

Get a cat.

I had a bird just like yours.
What I did was that held out my entire arm out to him, my fingers in a fist. He couldn't get a grip on my skin, which meant that he couldn't hurt me too bad, just a few scratches. I did this while holding a spray of millet in my other hand, trying to lure him onto my arm. After a while, I progressed to my finger, but he still bit pretty hard, just not as hard as he used to (I even grew thicker skin on my finger because he kept biting at it.) Eventually, he calmed down and went abolutely everywhere with me. He never wanted to go back to his cage, not even for bedtime. HE still didnt particularly like anybodys fingers though, he just tolerated sitting on my finger, because he didnt want to climb up to my shoulder.

Another factor that may be affecting the taming process is if you have any other birds. If you have other birds, your cockatiel may not want to form a strong bond with you. Also, all-seed diets and not enough peaceful sleep can make for an EXTREMELY cranky bird.

Personal experience