What a beautiful baby girl! She looks like she's developing just fine; she's even smiling for the camera (or more likely for her mommy who loves her so much and takes such good care of her)!
I just wanted to encourage you not to worry too much about the length of feedings. Some babies are really efficient, and it is certainly possible that your little one is. My son (who had the disorganized suck and was spending one and a half hours taking three ounces from an easy bottle) became a quick nurser once he mastered latching on and transferring milk. I remember nursing him at a friend's house (once we could actually go out in public since I didn't have to pump all his food!), and she commented on how fast his nursing was. It worried me at the time because I wondered if he was getting enough right at that moment. We were, however, still doing a weigh-feed-weigh routine on almost all his feedings, so after that I timed a couple just to see. After he had gone about 4.5 hours (a long sleep stretch in the morning), he nursed 7.9 oz in less than 20 minutes. His next feeding (three hours later) was 3.4 oz in about ten minutes. (He was about 2 and 1/2 months old.) I had a good supply but was not dealing with oversupply or overactive let down (I was nursing exclusively on one breast), and these are the numbers for a baby who had been spending 90 minutes getting three ounces out of a bottle three weeks earlier.
How sensitive is the baby scale you mentioned? Even if it measures down to half an ounce you can get a good ballpark figure of what your baby takes in when she nurses over a period of time (the weigh-feed-weigh routine). I'm sure I weighed my little guy longer than I needed to for his sake, but I did it for my sake. We had had such a hard time feeding him at all when he was born, I needed to see that my body was nourishing him wonderfully.
I will say about the sleeping, that my little guy did start to stretch out his feedings when he started nursing so well, and his little body put him to bed early in the evening (and often woke him up a lot during the night). Nevertheless, I usually fed him before I went to sleep at night. It got him some extra calories and me a little less fullness on that one side. We didn't do seven hour stretches, but if he wanted to have five hour stretches in the evening, I let him. I did find that he sometimes nursed better when he was so well rested and my breast was more full. (That could have just been peculiar to his personality and my one-sided nursing situation, of course.) I did ask the doctor if it was harmful to wake him up to feed him, and he was a little stunned at first because that's not the normal question people ask. He said that as long as he got several good sleep periods, it was okay to wake him up but to try to keep it to just a feeding if he was soundly asleep and seemed inclined to remain that way. That's what we did for a long time, and it worked well for us.
It really does sound like you and your daughter are doing well. I'm glad you're reaching out for support, and thanks so much for putting in a picture of your little one. She really does look beautiful.