Is There A Way To Give A Baby Human Milk And Not Formula After Birth?

I read that true breast milk usually comes in about 3 to 4 days after the birth of the baby; however, a baby needs to eat way before then. In a situation like this, what can a mother do if she wants to breastfeed, but her milk is not coming in until several days later??? (Note: she does NOT want to give the baby formula). Thank you.