^ I agree with his suggestions!

We should get her something ~magiciany~ to play with. Maybe some tools to play magic tricks with, or a magician costume?
Since we've been giving the girls personalized tees, we should give her one as well. Something along the lines of Arabian Princess, or Super Tall and Sexy Maknae or Super Magic Woman? o.o
For next year, we can give her a shirt that says 'Officially Legal' 
She loves being crazy with Bomi, so maybe we could give her funky, hip hop costumes to dress up with. Something like the costume the pair took a selca with:
But much prettier
Other than that, we could give her a notebook for her to write her school notes in it. The notebook could be personalized, like have little messages at the side on each page to give her the motivation to study (cause' we all know studying isn't the most fun thing to do anyway T_T)
Hope this helped! ^^ and thanks for organizing yet another birthday event for our girls