looking for opinion here... when in the hospital a nurse told me that once you give a baby formula,…

looking for opinion here...

when in the hospital a nurse told me that once you give a baby formula, it changes their stomach so they can't digest breast milk the same...yet everything else I've read says it's perfectly safe to supplement some formula in with breastfeeding so your boobs can get a break. I don't want to strictly put her on formula, but I'd like to add some formula to babygirl's diet. I'm just wondering if that's safe? there's a section in my breast pump booklet from Medela about how you can mix them both in the same bottle even, so I would think it's fine...Was the nurse just trying to push breastfeeding on me?