My DS has been a quick, effective feeder from birth (he averaged 10-15mins all up, longer feeds were 20-30mins). He's 3.5 months now and is finished in about 5mins (and he will only take one side), although he can feed a little longer overnight. I figure he must be getting enough as he is happy & content, demand feeds 3-4 hourly (he was going 2 hourly but he has stretched it in the last couple of weeks), and is putting on weight really well. If he weren't getting enough, I'm sure he'd be letting me know!

So your DD sounds like a totally normal effective feeder. If she weren't getting enough & wanted more, I'm sure she would be letting you know