^ It's actually how milk works! Kinda. Milk usually comes out of multiple (up to 20-ish) tiny little holes (hair-width?) on the nipple itself.
But for sure we can call it an artistic liberty, that the artistic took to have Rosaria spray like that from her areolae as well.
Aside from that, there are Montgomery glands on the areolae, which are tiny little bumps -- sometimes barely visible, sometimes look like tiny nipples next to the real one -- and their job is to lubricate and disinfect the nipple-areola region for baby to latch on. Sometimes they can leak a little milk but I understand they wouldn't spray like that.