The average feeding at the breast is around 2-4 oz. So smaller bottles would be more natural. Smaller bottles also mean that babies get hungry more often- which, again, is more natural- and therefore their moms have more opportunities to offer the breast.
It sounds like your baby is taking a normal amount from a large bottle, which is great- it means you're probably not overfeeding her, or that she has a good sense of her own satiation cues. Still, I'd decrease the size of the bottle. When the bottle is always full, baby will always take her maximum.