At about 3 months my DD started spitting up really badly after eating--almost projectile, in fact. Turns out she had pediatric gastroesophageal reflux --which sounds scary, but just means the valve at the top of the stomach was still immature. She outgrew the condition, as do most kids.
You might try making sure your DD burps well after eating, and try keeping her upright, or at least off her stomach, for a bit after eating to see if that helps.
Are you bottle feeding or breast feeding? In either event, are you letting her come off the nipple on her own and feeding her on demand? Those things should help make sure she's getting as much as she needs, but not eating too much and overfilling her little tummy.
Also, take a measured bit of milk, about a teaspoon full, and pour it on to a dinner plate. (I'd use regular milk or formula; I wouldn't waste breast milk for this.) That will give you an idea of how much that amount of liquid looks like if it's been spit up. Try it with other measured amounts as well. That will enable you to guess more accurately how much your DD is spitting up, so that if you continue to be concerned you'll have accurate information for your pediatrician. It can also reassure you if it looks like she's spitting up a lot, but it turns out that it's actually only a teaspoon or so, meaning her intake isn't really being compromised.