Babies spit up! That's normal. It's not like vomiting, which is more forceful and can upset your baby.
Check the size of the hole in the bottle's nipple. If it's too big, she may be drinking too much milk or formula. If it's too small, she might be gulping in air. When you hold the bottle upside down, just a few drops should come out. If it's more or less, you may want to try a different nipple.