Baby spit up?

So my 6 week old eats 4 oz per feeding every 3 hours or whenever she’s hungry. However she ALWAYS spits up her food. Which means she’s overfeeding right? But if I don’t give her the amount she wants she gets angry and does her rooting reflex so I don’t get it. We burp her before her feedings and after and slow down her feeding time by using a pacifier. So it can’t be gas or her eating too quick. What could it be? She spits up at least once per feeding and sometimes it’s through her nose.