J.W.
It is true, my peditrician said it was a wives tale that babies will sleep better on a full tummy...at 18m it's not the case. :) A couple of studies have been published that 4m may be too young to introduce solids b/c they are developing wheat/gluten allergies later in life. Babies are ready to eat when, they can hold their own neck up, sit up on their own and begin watching you eat, ie following your spoon or fork to your mouth, licking their lips are some good tell tale signs. www.wholesomebabyfood.com is a great website. If she is gassy, she has not developed the digestive enzymes to process the rice cereal. So it may be too early for her, try again when she is closer to 6m. I gave my daughter an avocado as a first food, it has good fat for their brain an it is super easy to digest as bananas and sweet potatoes, easier than rice cereal. Happy Baby Bellies is an excellent rice cereal as it is fortified with probiotics to help ease with digestion too.
Good luck!
J. W. MPH
Wellness Educator/Lifestyle and Wellness Coach