in laws and cereal feeding

So my little girl just turned four months, and the pediatrician gave us the go ahead to introduce cereal. Well we've been told to only try to feed her with a spoon and not put it in the bottle. Now my mother in law is saying "well that's ridiculous , I always fed my babies cereal in a bottle and it made them sleep." My girl sleeps through the night and has done so for close to two months now, so I'm not sure why they feel it's so important to feed her through the bottle. I also read online that it can cause babies to choke if they aren't used to solids. I told her this and she just rolled her eyes and said "that's  not true. Who is her pediatrician anyway?" And says all this in a pretty condescending tone. I'm obviously going to stick to what her doctor says, but I'm still annoyed. My husband told me I should hide the cereal in our house so that his dad doesn't try to feed it to her in a bottle during the day to make her take longer naps (his dad watches her while i work during the day). The fact that I have to do that is so beyond crazy to me. I'm very frustrated and I'm just trying to do what I feel is the best for my daughter. Just wanted to vent. 😡☹️