If she's gaining well and thriving, I guess I just don't understand that there's a problem. Is it because she feeds frequently, and stays on the breast a long time? It's normal and natural for a newborn to spend a long time on the breast, and to enjoy lengthy comfort-sucking after the milk has stopped flowing. It's also normal, natural, and biologically appropriate for a baby to prefer smaller, more frequent feeds. If baby is gaining weight at a normal rate, then baby is getting just exactly what baby needs. Yes, she will become more efficient as she grows and becomes more alert. Although some kids (like my DS) will always prefer to nurse more frequently, and many kids will spend plenty of time at the breast NOT actively "eating," because breastfeeding is about so much more than food.
So if I were you, I wouldn't worry about it. If baby is gaining well, there's no reason to supplement, and bottles can undermine your efforts. Sucking from a bottle is a simple matter of suction, and the milk comes easily without too much effort. Suckling at the breast is a complicated action of mouth and tongue. Some babies, although not all, will learn habits at the bottle that will make them nurse less enthusiastically and energetically, so that they're getting less and less at the breast, which leads to premature weaning and compromises your supply.
I think that with a healthy baby who's gaining, all you need to do is follow baby's cues. It can help a lot to learn to nurse with baby in a front carrier or sling, so that you don't feel like you're spending all day sitting around nursing.
me , he , my three , , and -- and the one we lost