Life of a Princess. Wait what? No, Life of a Loser
So if you are going to use animals at your characters, you have to remember that they don't have opposable thumbs and can't walk on two legs...unless you tell us otherwise. This means you need to write a little differently than you would if you were writing as a human.
As for the first entry in general...In every diary (or journal) that I have written, it's look, then age, then things I like, then family stuff. For the family things you have...it's slightly unrealistic to the point that is drags the reader away. Mother don't act like that, they pull the "Be nice, she's younger and doesn't know any better" line, but they don't intentionally favor one kid. or at least not so obviously. like with the pancakes things, it would be more "Oh, she ate them all, sorry." not "I purposely excluded you from breakfast. Deal." And mothers don't purposely try to embarrass their kids, so having the mom call out something that isn't true is unrealistic as well. The kid sister, though, seems more likely to do something like that.
Also, make sure you proof read through it, there are some confusing sentences and misspellings so just check for that. Always something to look for. As I have said before, reading it out loud is your number one way of checking to see if it makes sense.
Overall, it seems like it could be an interesting story and I am glad you have continued beyond that you have on chickensmoothie. I hope you keep it up!