G.K.
I do NOT agree with your pediatrician!! She's only 7mo!!!!!! Of course, she's going to be hungry a couple times throughout the night. Even adults can get hungry during the night... My 17mo daughter wakes once/night to nurse, and I know it's not a comfort nurse because she gulps and gulps for about 7-8 minutes, then falls back to sleep. If she weren't truly hungry, I honestly don't think she would wake because there are night where she sleeps 12 hours straight. (few and far between, but....)
I also don't agree with your pediatrician telling you to go cold turkey. I don't know your ped, but it sounds like he/she doesn't know much about breastfeeding if they suggested it. Going from 3 night feedings to none could not only sabotage your milk supply, but it could lead to engorgement and plugged ducts, which could also lead to mastitis.
At 7mo, both my kids were still nursing every 2-3 hours during the day, although at that age, they did start to taper off due to eating solids. 7mo is also a VERY big developmental age... just think of everything your daughter is learning to do... crawling, pulling herself up, speech, maybe teething etc. All that movement requires calories.....
I've never been one to pay too much attention to the percentiles, and I'm lucky enough to have found a pediatrician who doesn't ether. In fact, she doesn't even tell me what percentile they'e in; she pays more attention to the height/weight ratio, and even then it's only after age 2. Breastfed babies gain weight, and I LOVE fat babies! All that weight will start to come off when she starts walking, etc. Both my kids earned the "Michelin man" and "Stay Puft" nicknames and kept them through about 18mo (my daughter is sadly losing most of her baby fat, but at least all the 18mo pants are finally starting to fit!!! haha)
My opinion is to watch your daughter's cues and feed her when she's hungry. Maybe try to stretch out her night feedings or try co-sleeping (if you aren't already) to try to get a little more sleep. I don't have any suggestions for why she's awake for so long during each feeding, but how does she nap during the day? At 7mo, is she taking multiple naps still or is she down to 1 or 2? What time does she go to bed at night? What time does she get up for the day?
I suggest working on her daytime napping and feeding before starting on the night. Sleep begets sleep, and I hate to say it, but the better they sleep during the day, the better they sleep at night. However, it's a fine line to walk. Keep track of how long she's awake before she's ready to go to bed for the night, and wake her to correspond with what time you'd like her to go to bed for the night. Maybe that first night feeding can correlate with your bedtime?? I know this turned into a book, but hopefully you'll find something useful :)