Follow your baby's signs, not some chart of "this many oz at this age" -- 6 weeks is *prime* time for a growth spurt. Ditto for 9 weeks, and 12 weeks. Infants grow SO quickly in their first year, so it's not unheard of to have periods of wanting to eat more. For breastfeeding moms, it's called "cluster feeding" where they just nursed the baby, but the baby's hungry again. Just because a baby's getting a bottle instead of a boob, I'd still think "cluster feeding" would apply!
Also, you say, "would be great if I could stretch her feedings out some." While that might seem more convenient for *you* right now, it is definitely not as healthy for your daughter. Little babies have small, young stomachs that are meant to be fed smaller amounts, more frequently. It's really not a good idea to try and increase the number of ounces right now just to hopefully stretch out the feeding. She's way too young for that, in my opinion.
Lastly, sometimes babies do *seem* to ask for more food when really they're feeling some discomfort, whether it's a poop that's going to happen soon, tiredness and wanting to go to sleep, further on down the line it might be teething, etc. So just observe the next few times you give her that extra bottle - does she poop right away? fall right asleep? or is she awake and full and content? If you consistently notice that she's pooping or peeing (all of a sudden her diaper is warm), or falling asleep, then you can respond to those needs the next time *before* the extra bottle - rock her to sleep, hold her knees to her chest to help her get the gas or poop out (you can even take her diaper off and do this over the toilet - babies are born knowing how to do this, but we parents have lost touch with this because diapers seem convenient). If you feed her the extra bottle and she's just full and awake and content, you'll know it was likely hunger.
Congrats on being a new mom and on your beautiful new daughter!