About 2 ounces is good. I really agree with Mumma2many's remarks in regards to letting your baby nurse as often and for as long as she wants (most of the time it is for comfort and not for nutrition). If your nipples are just sore keep nursing her through it. But if it is toe-curling pain that does not relent as she continues to nurse you need to seek a lactation consultant's expertise.
My nipples always hurt when my daughter first latched on and after she suckled for a several seconds it eased up - it is NORMAL for there to be initial pain as your breasts are very tender. But the pain should relent. Pain does NOT always mean poor latch.
Please see a lactation consultant ASAP so you don't lose your breastfeeding relationship with your baby. ;-)
2 oz is a good amount for 8 days old. Some babies may take more or less though so if she is wanting more or less it's fine as long as she's gaining weight appropriately. As for nursing, you should nurse as long as you are comfortable.
Unfortunately some people, like myself, have major issues with improper latch. After 4 kids we STILL have not been able to get it right for many reasons I won't go into. I have always ended up pumping and bottle feeding breastmilk. Some people are able to perservere and make it past the sore nipples. Yes putting baby to breast often is the best thing for your supply, but if it is causing you an exceptional amount of pain, pumping is the next best thing....so long as you have a good, hospital grade pump...
Have you been to see a lactation specialist? If not, you should def. consider it.
Breast milk is like concentrate and formula is like fruit punch. She needs much less milk then formula. You should be letting her nurse as longed she wants to, as often as she wants to. The best thing for your milk supply is nursing. Nursing can be uncomfortable for the first little while as you both learn what your doing. BUT it should not be painful to the point your toes are curling. How is her latch? A bad latch causes 80% of breastfeeding problems. If you think it's painful, I'd call someone to evaluate her latch and see if that makes things better. Good Luck and hangin there! You won't be sorry!