Re: overfeeding and spitting up
You haven't raised a glutton. As the PP said, babies seek the breast for the most natural of reasons- because they are hungry, because they are tired, hurting, needful of reassurance, cold, sleepy, scared... This is just nature's design for human infants. It's why human milk is relatively high in sugar and low in protein and fat compared to the milk of animals who nurse only a few times a day- our babies are designed to feed frequently.
Growing a lot is normal during infancy. And it tends to happen in spurts- all of a sudden you realize your LO has outgrown all of her clothes. But again, as the PP mentioned, growth will start to level off at around 4-6 months.
The spit-up is normal and not a sign of overfeeding. It's more a symptom of baby having relatively weak muscle tone in the sphincters which keep stomach contents down in the stomach. Like all of a baby's muscles, those sphincters are fairly weak when the baby is born. But they will get stronger with time and spitting will likely decrease a lot once your baby spends more time sitting upright (babies usually master getting into a sitting position around 6 months- some will master it much earlier, some will do it later).
Don't worry about hunger signs. If you're ever in doubt about whether or not your baby is hungry, just nurse her! If she doesn't need to eat, she won't. Or she'll take a few sips and then be done. It's far better to nurse more often than baby needs than less often.
Mama, what is your primary concern? That you're nursing her too often? That she'll get fat? That you're hurting her development in some way by nursing on demand? Because none of these things are things you should worry about.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"