Since she is over 14 weeks old, she will be testing her boundaries and set the pecking order. At this time you are needed to bond with her as her companions, training will follow and honestly speaking you'll find that you don't need to train her to do things. Try and build a relationship with her based on trust, both you and the bird should trust each other. You may watch the TV sitting beside her (ok about 1 or 2 feet away), or may read a book or just sit and relax, let her accustomed to you being close.
When she nips or bites you, she is actually trying to tell you that she's the boss and also she's trying to know how powerful she is (physically). If I were you, I wouldn't offer her my fingers to practice, but you have devised the right plan by offering her seeds. Occasionally try to touch her beak (upper mandible) gently and, when you're assured that she does't mind that, hold her beak with your fingers, and give it a gentle shake and let go in about a second or two, this will teach her that your fingers and hands are not for chewing.
Good Luck
