Feeding baby

So I've been keeping it a secret from my sister that I've chosen to formula feed. She's the type of mom who breastfed and before I was even pregnant said she'd disown me if I didn't choose that..well my dad slipped up and mentioned it to her 🙄 I am a first time mom, only have my dad and sister on my side of the family now, and am now dealing with her telling me how awful of a mom I will be. Saying how I am already choosing to not do what's best for the baby. I am not researching enough to prepare for a baby..so on and so forth. Literally the hardest thing a first time mom can hear about her first big parenting choice is being told she will be a terrible mom just because she has a different opinion :/ so word of advice, if someone you're close to doesn't ask for your opinion on a parenting choice, don't give it lol just be supportive!