You cannot overfeed a BF baby. They will let you know when they're hungry and eat until they're satisfied.
Babies typically have growth spurts at 3wks and 7wks and will naturally nurse more frequently.
It's imperative in the first 6wks not to limit feedings to insure a good milk supply. Letting baby nurse whenever and as often as she likes will go a long way in promoting a successful BF relationship.
Spitting up isn't a concern unless baby is not gaining weight (and they can spit up A LOT before that ever happens

).
It sounds like you're doing a wonderful job and baby is doing fine. She won't be BF every hour for long. After the first six weeks you can encourage baby to go longer between feedings if it's becoming too much for you and she doesn't seem to be lengthening out her nursing times on her own.
Kelly