Coworker donating her breast milk to my baby

Michelle • Baby 💗 born 6/11/17 & 💗 born 8/27/19

A little backstory. I was only able to nurse my baby girl for one week. I hemorrhaged one week PP.. was separated from my baby for days. I was given heavy medications to save my life. I could not pump or nurse for her because of these meds. It was heartbreaking on so many levels. Anyways..my coworker was able to provide breast milk for her baby for a whole year. She still has 1000’s of oz of breast milk that is going unused. She has offered to donate it to me. I trust this girl..I’ve know her for years. She leads a healthy lifestyle. Has anyone used donor milk before? Since my baby has been on formula for 6 months will introducing breast milk bother her belly? I am so grateful for this girl. 💗💗