Piercings-for the girls?

No, the milk doesn't come out of the piercing holes too. It's the same as why saliva doesn't come out of lip piercings and snot doesn't come out of nasal piercings, the skin sort of closes in on itself.

One thing to point out though - nipple piercings can help with breastfeeding - obviously you remove the piercing when feeding little baby, but the nipple piercing can make the nipple stand out more which is helpful in breast feeding as the baby can get a better grip and you don't need nipple shields as much.

That depends on what gauge the piercing was done at and how long the piercing has been there. An 18g piercing (the size of the stud any girl would have in her ear) wouldn't allow for liquid to pass through it, while a 14g piercing would be much more likely to seep breast milk from the piercing site. Also, the longer a piercing has been there, the less likely it's going to "close" because the skin has healed up. If a piercing is relatively new, it'll somewhat "collapse" and make it harder for anything to pass through the piercing entry way.