Children’s fantasy Picture Book from the early 2000’s about a girl dragon helping a knight

Here is what I can remember about it:

Genre: children’s fantasy

Format: Hardcover picture book

Setting: medieval Europe

Time: I read it in the early 2000’s but it may have been from the 90’s, I can’t be sure.

Premise: A younger teenage girl dragon with tiny wings that don’t work fights with her bigger brother at the beginning of the book. He doesn’t want her to help a knight and he makes fun of her little wings while he flies and she’s on the ground near a cliff edge. she tells him off with a huge breath of fire, he gets a comical sort of singe to him and then she blows a little puff of smoke at him in the shape of a heart letting him know she still loves him even if he’s a bully. The knight is very lanky and skinny with a long mustache and full metal armor. He doesn’t want to kill a dragon but he wants to marry the princess in his kingdom so he was asking her for help to help win the royal families favor without doing any harm to another creature. They plan to have her play dead when they get to his kingdom so he can marry the princess but when they get there she hears how the king and queen bully him and she gets out of his cart and scared them into treating him better I don’t really remember the end of the book but if anyone has questions I might be able to answer

Thank you so much to whoever takes the time to help or read this all the way through, I’ve been searching for this book for over a decade with no luck, and it was my favorite book as a child