Help with MIL

So my Mil doesn't come around often but yesterday she did, my baby is EBF he doesn't even take a binky. So his grandma brought over bottles and I told her we don't use those & she started telling me how selfish I am that I'm not letting anyone else bond with him because I won't let people bottle feed him. Please tell me how I'm selfish for this? He's a breast fed baby I don't get how this is selfish. & then my baby's dad was agreeing with her!! I've never been so pissed in my life excuse my language! But last time I checked this baby came out of me not her. Do you think I'm selfish for not allowing people to give him a bottle when I only breast feed? This happened yesterday and I thought about it all night and I'm still upset today mainly bc my SO didn't back me up 😭