There's vomiting, and there's spitting up. Vomiting is a symptom of illness. Spitting up is normal baby behavior, and in the absence of pain is a laundry problem, not a health problem. It can be caused by fast feedings without enough burp breaks, but it can also not have a cause other than the fact that the muscles that keep stomach contents down are weak in babies.
Often mamas get freaked out by normal spit-up episodes because the amount that comes back up seems so large. "Seems" being the key word. By 12 weeks, most babies are taking between 2 and 4 oz at the breast. Measure 2 oz of milk (cow's milk, please, not your own!) and dump it out on the counter, and when you see how that spreads out you will probably realize that the amount of milk your baby spit up is not as big as you thought. Which is my long-winded way of saying that even if your LO spit up a huge amount of milk, she may still have quite a lot in her tummy.
You can always offer to nurse after a baby spits up or vomits. If the baby is hungry, she will nurse. If not, she won't.
Bottles of EBM should probably follow the 1.5 oz/hour rule of thumb. A lot of breastfeeding moms seem to leave bottles which are on the smaller side- 2-3 oz- and have their daycare providers feed the babies frequently.
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!"