M.W.
How many ounces are you feeding her in the first bottle???
Formula or breastmilk???
Babies go through growth spurts but it is not normal if she never seems to get full....... At 6 weeks, I'd say 4 to 8 ounces would be a "normal" range at a feeding. If it's formula, she should be fairly satisfied for 3 to 4 hours. Breastmilk, it's more like 2 to 3 hours. Make sure you are mixing the right water to formula ratio if you are feeding formual. That could throw her off otherwise....