It's hard to know what to do when everyone has a different opinion. I think it's good to read widely and take in all the different ideas, but ultimately be guided by your baby.
In addition to the question of whether she's ready to eat (and remembering you can't actually see what her digestive system is doing right now), I think you need to consider whether she needs to eat right now. For most babies, breastmilk provides all they need till at least 6 months. And when you introduce solids early there's a tendency to replace milk with solids, but the sorts of things that are introduced early on (like that cereal) don't provide the same sort of nutrition as milk.

Have you read anything about baby led solids? I like this philosophy because it allows babies to lead the way in what and when they eat, so you have greater confidence not only that their innards are ready, but that they need the food - they eat when they're hungry. It's also easier than cooking and pureeing separate meals, as you just give them access to things that you are also eating.

The choice is yours and you'll figure it out with your baby. If you're really not sure, I'd suggest taking a BLS approach and letting your DD decide for herself. She probably won't be eating for a while yet if you do that.
Oh, and just in case - don't feel bad, ok? It's fine to change your mind when you get different information.