Breastfeeding ladies !

First time mommy here and my daughter just got out the NICU, well they were giving her the little drops of milk I was pumping out with her formula and now since she's home I decided to give her a bottle of just my breastmilk since my supply has came in. She spit up 3 times. Is that normal? She's never spit up with her formula. I'm so scared to give her my breastmilk again it makes me want to just stick to the formula! Any advice please..