The theme was to portrait her as a Griffindor magician summoning her complete-form patronus. For those non-potter fans, a patronus is a protective light spell that can take the form of an animal in its strongest form. It is specially good against dark things, and it is learned by Harry during the third book/movie.
Since the Spell is mostly blue-ish light, I worked with a palette of white, a couple tones of blue, grey, purple, and a bit of red. I started painting the base colors first. Then, I used water to blur the blue and create a gradient. Later on, I added other tones of blue and purple to shadow the magic. I worked on the girl after that and added little details on the bear for recognition. When everything was done, I embedded the brush with white paint and splashed white dots and lines over the spell trajectory and the bear patronus itself.
This is the final result. She loved it pretty much and now uses it as her phone wallpaper. I hope you like it too -even if you are a muggle XD.
Work done on a 210x297mm, 180gsm, acid free watercolor paper, and painted with tube and Pan watercolors.
Photos taken with a Redmi note 7 camera, and edited with Snapseed.